Will I need to leave my computer on?
If you plan on streaming audio to the SHOUTcast server yourself, then yes. For as long as you want the server to be broadcasting, you will need to provide the audio live for it to broadcast.
However our Auto DJ doesn't require you to connect yourself, as the Auto DJ will connect and stream on your behalf. You will simply need to upload audio in the form of MP3s in the client area and enable the Auto DJ. It will play the MP3s you've uploaded and you'll be free to use your computer as you like.