On the Drum Machine app thing?
Okay, I don't remember all the names of the buttons, so bear with me. If you're on there now, push the button on the far right (above the time table thing) and then there should be an option saying "record as mp3" or "export as mp3" or something. Once you push that, it will immediately start recording your piece. Just hit the "stop" button when you're finished, and it will download as "drum.mp3." Then you can name it and edit it etc.
I did the fade thing at the end with a different program, though.