First you'll need to upload your mp3's to your new server. This can be done 2 ways, Web Based Uploads are performed in your browser, find the mp3 you want to upload on your computer and click upload. The second method is via FTP Client such as the free Filezilla. Using FTP method allows you to upload several mp3's at one time.
After you've uploaded at least 2 mp3's to your new server, you can simply add them to the "Heavy Rotation" playlist or you can begin to create and schedule your own custom playlist such as the "Weekly Top 10"
If you performed the above steps correctly you should now be able to start your server. Other listeners can tune into your stream using just about any other type of media player such as Windows Media Player, iTunes, Quicktime, Realplayer, or the built in flash player.