Sure thing!
You're missing two things:
1. A Source Port (Which is the application you're missing)
The mod should tell you what source port is required in either the post/place you got it from, or in the readme.txt file that came with it. (Assuming such a file is included). If you can't find that, I believe most mods use GZDoom, which you can find here:
https://zdoom.org/downloads.
2. An Iwad to go with the wad from the mod you just downloaded.
It should also be mentioned by the source you got the mod from. If it's not, an Iwad is generally the wad that comes with ChexQuest or ChexQuest3. ChexQuest's wad is called "doomu.wad" or "Chex.wad", while CQ3's is called "Chex3.wad". If one doesn't work, you can try the other.
Chex.wad Link:
http://gallery.xboltz.net/downloads/ It's a bit hard to find here, but you want ChexQuest.zip (I think). The download section here seems to broken, so this is the only proper one I could find at the moment.
ChexQuest3 link:
http://www.chucktropolis.com/gamers.htmNow all you really need to do is have all these files in one folder, drag the mod's wad file onto GZdoom.exe and it'll run it, then it'll ask for an iwad (It should provide a list, choose which one you want). And play. If the mod you downloaded came with a .bat file, you can try running that, which will attempt to do the same thing as drag and drop.
Long Answer:
Sorry but you are not allowed to view spoiler contents.