how?

[ColourTheory]

How do I make textures?

[Fat_Sacks]

What do you mean? Actually draw the textures, or using them?

[ColourTheory]

use them

[Fat_Sacks]

Go to the editor, insert the block, or whatever you want use and then insert a texture into that. After that paste in the image link into the texture.

Read the wiki post if you want to go more in-depth.