Welcome!
Step-by-Step guide to create a Custom URL for your YouTube Channel
Eligibility criteria to get an option to set Custom URL :
=> Your Channel should have 100 or more subscribers.
=> Your Channel should be at least 30 days old from the date it was started.
=> Your Channel should have an uploaded profile picture.
=> Your Channel should have an uploaded banner image (that is, Channel Art).
After you met all the above conditions, you can go to YouTube Studio
https://studio.youtube.com/
(Please remember to select the Channel to which you are going to add Custom URL).
In the Left Menu options,
=> Click on "Customization" menu, then you will see three tabs "Layout", "Branding", "Basic Info"
=> Click on "Basic Info" Tab, then you can see a section named "Channel URL". That is your default URL. It is created by default when you started your Channel.
Below your default URL, you can see a link like this "Set a custom URL for your channel" (or a Similar text)
=> Click on that link, then it will show 2 options
1) https://www.youtube.com/_Your_Channel_Name_Here_
2) https://www.youtube.com/_Your_Channel_Name_Here_ and a Textbox to type letters or numbers after your Channel Name.
Select 1st option if you like to have that URL or else you can select 2nd option and add letters and numbers to your channel URL.
(Please remember, think many times before setting your Custom URL, because, once you set, you cannot change it. So please be careful and check spellings)
Note : if you want to change your Channel Name, then change it before setting Custom URL and come back here and YouTube will automatically show your New Channel Name as Custom URL.
After selecting the desired URL, click on the "Publish" button.
Hurrayyyy..!
Now your channel got a Custom URL. you can share it with others and show it in your social media and also on Visiting Cards and wherever you wish to display it.
Note : If you don't see a link to set Custom URL after you met all the conditions, then please wait for atleast 15 Days (meanwhile, you can check whether you got the option or not, everyday). Because, YouTube Algorithm is taking some time to activate that option after all the conditions met.
Hope this helps.
Best wishes,
Pratap Reddy,
"Telugu Soft" YouTube Channel,
https://www.youtube.com/TeluguSoft