Why don't I have a custom title by now?!
if I drag and drop acheron2.wad into zdoom.exe, and the iwad selection box opens with four choices, ultimate doom, doom 2, plutonia, and tnt, which one do i choose and more importantly, what's the next step? If draggin and dropping is as simple as it sounds, then it's not working. If I have only one iwad in the same folder as zdoom.exe, and one custom wad, and I drag the custom wad into zdoom, it just loads the iwad.
Drag and drop acheron2.wad on zdoom.exe.
On the IWAD selection box, chose "Doom II: Hell on Earth".
The next step is where it might be puzzling. Acheron2 does not replace MAP01, so if you just start a new game, you will end up on the familiar Entryway, and it might seem like the mod wasn't loaded. In fact, it is MAP03 which is replaced! So you have to use the idclev03 cheat (or, in ZDoom's console, type "map map03").
Many old mods (and even some recent ones) are set in slots other than MAP01 or ExM1. The reason was sometimes as simple as because that was where the mapper's favorite MIDI was being played, and sometimes a bit more complex (certain maps have certain special effects, such as MAP07 having the scripted mancubus/arachnotron effect, or MAP15 having a secret exit). If you do not know which map is being replaced, it can be confusing.