Connect your Makey Makey Module to your computer via the micro USB cable. The micro USB does not supply power, so make sure to plug a power module into your Makey Makey module.
Set the "space/click" switch to "space"
Use one alligator clip to attach the spoon (or other conductive material) to the Earth port.
Use the other 3 alligator clips to plug 3 oranges (or other conductive materials) into the left, right, and space/click ports.
Go to http://makeymakey.com/piano/
Hold the spoon (connected to the earth port) in one hand, and use your other hand to complete the circuit by touching the oranges. Each orange will correspond to a note on the Makey Makey piano.