Was wondering what file to put a mod in when i download it

Erm... Like, how do you play a mod? If it's a .exe file, you need to get a downgrader, downgrade to patch 1.15.1 (usually), and run the file. If it's a .mpq, open MPQDraft, select the .mpq, and then select Starcraft.

Oh, this should go in Modding Assistance or Modding Discussion, btw.

You can put it anywhere.

(he wants to know where to place a downloaded mod)

So i can put it anywhere in my starcraft file?

Yes.

It doesn't have to be in your starcraft file.