In order to listen to music using our little service, you'd first need to download Spotify to your computer. You can do that right here.
Then, when that's on your computer, open it up. You should be presented with a login box. Pop your details into here, and Spotify will open up. Here, you can search for any song you want, build playlists, and share tracks with your friends. You can find out more about what Spotify can do here.