I've read your tutorials but I still don't really understand how to add textures? Please help?
A general process would be:
Open the texture in Photoshop (File > Open) or drag it
Prepare the base of your graphic in a new canvas. This is a background and a image/images, basically
Drag the texture/s to the new canvas and place them
Most used blending modes are Screen/Lighten (if your textures are dark) and Soft Light (both dark and light) and Multiply/Darken (light textures). Then you can modify opacity too That's in your Layers Panel. Select the texture layer and change that
Use the Eraser Tool (pick a blurry one and variate sizes) to remove parts of the textures that need to be removed (because their borders are noticeable, because they are covering someone's face, etc)
You can try putting the textures over/underneath the rest of the layers, for example the coloring layers, the pictures or the text
Important: most textures won't fit at the first try. Don't ever think you are useless just because you weren't capable of combine the textures you chose at first.
The graphic tutorials I made are very basic and easy to follow, in case you want to check (x) (x)