This is meant to be a multiplayer mod, meant to play with friends in a Deathmatch. make or find a server that has the FIAN (FPS IN A NUTSHELL) content in it and battle against your friend or other players or goto console and put "MAP MAP20" if you want to play the normal doom levels or get ultimate doom and play an unfinished campaign mode. Also, Check the addons for stupid or useful stuff. if you already have an extension map pack then you cant play on the normal doom maps.