Ok, download and install the client (program) from
here, it's just the number (on this date) '152' hyperlinked straight to the file.
After you've installed the client you will be asked to pick a username and password, choose whatever you like and then it will ask you what files you want to share, giving you a list of the drives on your pc with tick boxes next to each, DON'T TICK THE BOX NEXT TO YOUR 'C' (hard) DRIVE. Just click the '+' sign next to whatever drive that the files you want to share are in and then ONLY tick the box of the folder that you're sharing.
After that it will click ok and it will take a bit of time to index your files. When it finishes you'll see a large window and two smaller windows to the right of that. The top smaller window is where you add usernames. Right click in there and type the username in the box that comes up exactly as it is on here, they're case-sensitive.
When you've inputted a username or two, you can right click on the name and 'browse files'. It'll open a new window to show you a folder that you can browse. Have a look, pick what you like, highlight them, right click and choose 'download file'.
Alternatively you can just click the 'Search files' button at the top, type in the name of the group or track and see if it's available. The ones in grey are users that have no download slots available at the moment, the ones in black are available immediately.