You got a mix on yer PC (mp3 or wav stylee)? If so, you just need some webspace to host it. Otherwise, you need to get a pc/lappie hooked up to yer amp (line-out of amp into line-in on yer sound card) and record it using Soundforge or other such software, then compress it into mp3/real media or whatever and flutter yer eyelashes at someone for hosting..
You got broadband internet access? Makes things shit loads quicker...