Custom Textures

How can I make custom textures in Paint for example, and import them in? I tried the additional textures from directory or whatever but they dont show up, I just need to now how to make them on paint, and use them. Thanks.

You will need a wad editor like XWE or Wintex to import textures into your wad (or an external resource wad). Wintex is old and outdated and I wouldn't recommend the use of it. You want to add them between the PP_START and PP_END lumps, or if you're using a ZDoom based port, use TX_START and TX_END.

See the proper structure in my resource wad:

Last Man On Earth