There is a readme file included with each Doom conversion. Read this file to see which version of Doom is required and how to install the files.

*Note*
Doom 2 conversions may require version 1.9 of the doom2.wad. Most conversions worked before I upgraded to version 1.9. If a Doom 2 conversion doesn't work, try patching 
your doom2.wad to version 1.9. The patcher can be downloaded from here: http://dumped-archives.ath.cx/zdaemon/iwadtools/