Press Control+J to cycle through the three joystick emulation modes: "No
emulation" (default), "Right Joystick" and "Left Joystick". Use cursor keys +
Alt for firebutton. e.g., Tea Time uses the right joystick, so you'll have to
press Control+J once. Sorry, there's no feedback about what mode you're in
just yet.
Lots more to do: machine selection, tapes and disks. But for the moment,
here are a few games: