Reddit started out as a place for RandomJoeBobUser to post a link they found interesting, and let others discover that interesting link/content through that link. If people thought it also was interesting, they would upvote it, and it would move higher in the list of recently posted links.
Originally, Reddit's own rules discouraged posting your own content to the site (but did not ban, instead encouraging a 9:1 ratio of <other content>:<your content>). This was partially because that's advertising and they could be selling that advertising space, but also because people don't generally like ads mixed in with their 'list of actually interesting content' and they didn't want the place overrun by self-serving bots and corporations. You can see a reflection of this in Rule 2 of their rules, but adult workers posting links to images of themselves is entirely normal for the site.
Links can only be posted in subreddits, and those subreddits are generally themed around a certain topic. Technology posts in /r/technology, Minecraft in /r/minecraft, nude selfies in /r/gonewild (hosted offsite in the beginning because Reddit didn't host images, and now ), erotic hypnosis in /r/EroticHypnosis, etc. (Technically, you can make a subreddit called '/r/guzumptomini' and say it's for posting content relating to third century Egyptian art. The name is not a rule, as you will see later.)
So going into Reddit with the understanding that much of it is NOT about 'you', but is about 'topics' and 'themes' is a helpful perspective and understanding to have. It's not Twitter. It's not Tumblr. It's not Fetlife. It's about "content aggregation". It's not about you, it's about the content. If you want to post bimbo content, there's probably several subreddits for that, and depending on what else is going on in that content, it can be posted to a bunch of other subreddits, too.
Links shown to you on Reddit come from the default selection of subreddits you start out subscribed to by default as a new user. If you don't want links from /r/TwoXChromosomes showing up in your feed, unsubscribe from that subreddit after creating an account.
They may also have an algorithm style insertion of links for trending posts or suggestions based on what you interact with, but that can result in content showing up in your feed that you don't want to see. Mine's off, so I *only* see content from subreddits I'm subscribed to. Hence why I'm less sure about their injection of other links: I haven't seen it in years. It may be on by default.
If you are only subscribed to /r/aww, and all 'suggested' insertions are off, you will only see content posted in /r/aww. This is how you control your feed of content you see.
Almost every subreddit was started by a user, and users selected by the owner of the subreddit to be moderators moderate the subreddits in their own time.
Reddit Admins are the people responsible for policing the general rules of Reddit as a whole, and generally don't interfere in moderation decisions. But they absolutely will ban someone for saying (with seriousness) "all <gender/sex> are a disease" anywhere on the site. I've seen it happen, and am thankful for it.
Each subreddit has its own rules; for example, if you sell content online *anywhere* and you post a nude selfie in /r/gonewild? You'll be banned from /r/gonewild so you can no longer post or comment there.
Subreddits being run by users mean that a subreddit can be about a different topic than what its name may imply. For example:
/r/conservative is practically nothing but Russian Propaganda and you will be banned if you question the current narrative.
/r/trees is about marijuana,
/r/marijuanaenthusiasts is about trees,
/r/treelaw is about stories involving people facing justice for harming trees that don't belong to them (though it has slowly changed over the years to also become a place for legal advice about trees).
And /r/legaladvice is significantly populated by police giving out bad legal advice, as well as armchair "lawyers" with no law experience or degree handing out incorrect advice with ChatGPT-level confidence.
The rules for each subreddit are posted on a 'sidebar' in that subreddit. Sometimes the rule is "don't post content that goes against <link to long list of banned content>", and you'll need to click the link to see whether or not your particular kind of content is banned. There are many many subreddits that allow for posting adult content if you are a seller; /r/gonewild is simply explicitly for non-commercial users, because that's what the people there want.
Technically I believe uploading adult images to Reddit is disallowed, but I believe there is little to no enforcement of this? But to do so you may need to find workarounds past any part of their interface that prevents uploading images to something marked NSFW. It's easier to post the content elsewhere and link to it; Redgifs is the commonly used site for this purpose. Other sites may be auto-blocked by moderation tools.
Soundgasm.net was originally made for /r/gonewildaudio, and is generally the place most people will upload adult audio.
If you want to post your own content to Reddit, there are two or three avenues. Keep in mind that I don't post my own content, so I'm describing this based on my general impressions I have from seeing what others do.
One is to post it to your personal profile. (You can pin a couple things in this as well, and sellers will generally have at least one post that is either a direct link to where you can make purchases of their content, or a text post similar to a pinned post here on Tumblr.) This content is basically only seen by users who visit your profile, and may or may not get a lot of views. (The newer Reddit interface may provide for more notifications about content of this nature, but many of us still use the old-school interface, which does not.)
Secondly is to post it to subreddits relating to the content. Hucow themed? /r/hucow. But also maybe /r/erotichypnosis, /r/lactation, etc, depending on if there's a thematic link. And each of those subreddits has their own rules which may or may not allow your content. For example, you can only post self-promotional material on /r/erotichypnosis once a week. (That subreddit is much more for discussions around the topic than it is for porn.)
Posting to subreddits people are already subscribed to is generally how you draw people into your profile, and eventually your own subreddit if you have/want one. If comments allowing mentioning your content are allowed on a subreddit, a user may post a comment pointing people to their content on a link they posted (but I rarely see this, so I suspect many subreddits do not allow this).
The third option for posting content is to create your own subreddit (typically named after your username on the site OR a username you're well known by on some other site) and to post your own content there. Keep in mind that I have the firm impression that if you do this, you must *actively* respond to any messages sent to your moderation queue by users, or Reddit will eventually decide that your subreddit is unmoderated and ban it. And people won't generally 'naturally' find your subreddit unless you're posting your links to something they're already subscribed to, and they look at your profile to see the content posted to your subreddit as well.
Finding appropriate subreddits to post content in is likely going to be the first struggle. Google can help, but so can finding other users who post content similar to yours, checking out their profile, and seeing if any subreddits they're posting to fit the 'theme' of what you're aiming for.
(I have little to no experience or understanding of Tumblr, so I have no actual idea if this response will be seen.)