On the bottom of the page there should be a select box where you can set up the MIDI port of your interface.
Hit some keys and turn the modulation wheel. Wiiiiouuuu...
If you hear no sound check this:
Be sure that your MIDI Interface is switched on and connected to your computer
Be sure that your keyboard is switched on and connected to your MIDI interface
Be sure to use the most current version of Google Chrome
Turn up the volume
MIDIfy your own synth
If you want to configure your own synth just drop the Pittsburgh Midi module to your custom rack. For classic functionality you should connect the MIDI modules CV output to an oscillator 1V input and the gate output to an envelope gate input. But since it's a modular synth you can patch as you please.