/vr/ - Retro Games

>>5251485
You'll learn.
First, make a copy of your .wad (always make a copy before making a really substantial change, actually), then download Slade.

Open your .wad with Slade, then look at these tutorials:
http://slade.mancubus.net/index.php?page=wiki&wikipage=Tutorials

Don't use Slade for building maps though, that's just clunky, use Doombuilder 2 or something like that.
Slade is for managing and editing your code, textures and sounds, etc.