You take the wave that you get out of your recording and you convert it (compress) it into a mp3. Use the standard settings in your mp3 compression program and you'll have a 70 mb files out of a 500 mb one. Settings = 128kps mono is fine (and before you lot tell me he needs stereo, I want to know what dnb tracks are true stereo).
Sorry mate, but this is absolute basics.
I thought you were asking how to compress/normalize a mix so its all the same level but if you don't know how to convert files then audio mastering is not something we can discuss.