Prep Ground Wires
Next up, we need create short wires that will connect all the buttons ground together in series. We'll need 8 pieces of 30AWG silicone-coated stranded wire that are about 5-10mm long. Strip both ends of each wire using wire strippers. Use the helping third hands to secure wires while tinning.
Here's the full set of 30AWG silicone-coated wires all cut and tinned. They're short and thin!
Insert each ground wire into the through-holes before soldering into place. You'll want to assess the placement and double check the front and back of the PCB. In this project, I'm using the right side of the buttons terminals as the ground - so all of them need to be this way. Note, once the PCB is flipped over, the 'right-side' becomes the 'left-side'. Take this in consideration, as it can start getting confusing. I myself had to resolder a few times!
Solder Ground Wires
Apply solder to the designated button input through-holes. Ensure the wire is soldered to the correct through-hole on the power/ground rail. Use tweezers to assist you while heating up solder and inserting wires. You'll need to connect the top and bottom ground rails together by wiring up a piece of wire.
When you've completed soldering ground wires, snip off any excess terminals/wires with flush diagonal cutters.
And now we have ground wires! Double check your connections and ensure the polarity of each button is correct. If you managed to miss one, go back and heat up the pin, remove wire and try again. The Perma-Proto PCB has a high quality solder mask and copper through-holes, so you can do several attemps.