Stuff you need:
Download Doom 2 wad file
Download Doom Legacy zip
steps:
1. Make a new folder, and unzip Dc6.zip into it.
2. Put doom2.wad into the folder.
3. Run the program "LAUNCHER.EXE"
4. Specify the location of LEGACY.EXE and DOOM2.WAD in the Game Options Folder
5. For Single Player, click Launch, and for Multiplayer, click Multiplayer.
you need to do IPX, and have the right number of computers playing in the game. the game can't start until all the players have joined, and it has to be the number specified by the server.
NOTE: Doom2 has been released as open source, so don't worry about it being illegal.
to learn more: Doom Legacy Homepage
For Macs
You can get MacDoomLegacy at Doom Legacy Homepage. it's much much easier to configure, and OpenGL works properly on it, so the graphics are smoother. unfortunately you can't join PC games. you will need DOOM2.WAD as well though.
have fun
