You can find a lot of them by searching on Google, DuckDuckGo, Youtube and etc.
GZDoom, which's the definitive source port if you wanna play DOOM with mods - Download It Here [.I recommend you install either one of the following or use Windows' default Notepad: 7-Zip, in order to extract stuff - Download It Here [.You can get the complete collection here on Steam - Doom Classic Bundle Steam, of course, with all the classic DOOM games installed.What you'll need for this guide ( all links are free from malware):
