Reply to [BUILD LOG] - First DIY Build - Numpad Mod

I realise there's a few people taking this mod approach at the minute and a few new logs started up, which is a good thing I believe!

Anyway, here's my log. The intention of this log is to show to people that beginner's can make mod controllers. As a background, I have no experience of modding nor of any electronic work. So, if that sounds like you, follow this log if you wanna make your own mod controller. This one will be a 4 x 4 grid in the Midifighter shape for 8 cue points per decks, hopefully with LEDs.

Here's the numpad that I'm using.

This is my first post, and I'm needing help already!

I'm wondering how I will be wiring the buttons to the brain and how I can calculate what connects to where. There are 4 pics attached. They are front view and rear view of brain, the keypad with the underneath plastic layout part (which was folded up in half and had a ribbon connector that slot into the connector socket) and then one of the plastic part opened out.