Step 5: Solder Pin Headers to Leads
Once you’ve got the connectors wired up, strip the other ends of the wires and solder the leads to pin headers. This will let you plug them in to the Arduino easily. If you didn’t get the pin headers, you can try carefully tinning the wires to make them stay in the Arduino pin holes better.
I attached some wires to the pin headers on pins 11 and 13 of the iPhone breakout board. The Black wire is to Ground (pin 11) and the Red wire is to VCC (pin 13). I’ve then soldered pin headers to the leads for the two wires from the breakout board and the four coming from the PS/2 connector.