Connect two wires with P1 and P2. If available use a power supply unit with current limiting (50 or 100mA). If you don’t have one and you are sure that you don’t have not produced any short-circuits, you can also use rechargeable batteries

To attach the ground clamp of the probe without producing short-circuits i recommend to remove a little bit of isolation from the minus wire to the voltage supply. So you can use any alligator clip.

Connect Pin 2 and 3 of the socket with a 1k resistor. This activates the integrated testprogram.
Set the oscilloscope to 1ms/div.

After you have connected the power supply unit, at pins 24-28 and 30 of the Mega8 you should see the 5V square wave signals shown in the picture below with the oscilloscope. There are small peeks in the middle of the 2ms signals. These are not shown here.