Welcome to Ben's Doom WAD editing page. If you're new to WAD editing, get the Wad Constructor's Handbook (available on-line) and a copy of a WAD editor. Read the handbook and any documentation with the editor. Learn from your mistakes and if you're stuck either look at one of the original DOOM levels, write off to rec.games.computing.doom.editing, read one of the tutorials (available from the mirrors below under doc), or look at the Q&As below (written by Lee Killough)...
p.s. some editors allow you to edit shareware Doom but you will need a registered version to save and play it.....