RUN IN TURBO MODE (SHIFT-click the green flag) Click with the mouse to put squares. Press z to toggle between alive and dead cells. Press space to start the simulation. When it asks for c, set it to 1 for a random "seed," set it to 0 to make a predefined pattern by hand.
Why did I use Seeds as a base? I don't know. It would have been easier to start with Highlife. Oh well, I got it done anyways.