Make sure to include the 4 pins on the bottom panel too! After you do one side, use the remaining ground daisy chain to connect all the other button to another ground pin. They will chain together, and the order is not important.

Plug the female header pin into one of the ground pins on the USB board, and then connect either side of the player board ground pins together. After all the button pins are wired, use the wire with a daisy chain of spade pins and 1 female pin to make the ground connections. You will be plug in the corresponding USB pin into the middle pin of the button. The closest one, which is the ground pin, the middle one, which is the input pin, or actuating pin, and the bottom pin which is closes to the wood and is NOT used. Although the exact order isn't critical, it is critical that you don't use aground pin (GND) for a button pin. As per the diagram, wire up all the connectors to the USB board. You will also have 1 set that has 2 female connectors. Start by separating out the wires and finding the ones that have the 4 pin female connectors on one end. Again, you can always adjust it afterwards. Follow the included diagram and you should be fine. It's actually fairly simple and the specific layout can be adjusted via software on the Raspberry Pi, so exact locations of the represented A, B, X, Y, etc., is not that important.

Micro center dual monitor stand