Full instructions are in gadget. Lay down your drum hits by clicking the blue rectangles, set your Beats per Minute and go. 4 steps per beat.
When you first set the machine playing there will be a bit of lag for the first couple of seconds (and immediately after setting/unsetting a hit) but it will quickly settle down to a steady rhythm. The less tabs/programs you have open the smoother the drum machine will play so shut down unnecessary surfing for the best experience.
Patterns are saved to your clip board. Simply copy and paste.