The default program on the board just sequences through all the channels. But it’s very easy to write your own programs and upload them to the board.
If you want to remotely control the Sequencer from a computer via XBee, here’s a simple program I wrote while testing out the prototype. It waits for characters on the serial port (this could be from the serial console or an XBee) and turns channels on and off. It uses the “qwerty…” keys to turn channels on, and the “asdf…” keys to turn channels off, so if you’re using a keyboard it’s a bit like a piano. Hopefully it will provide a starting point for you. Good luck!