Raspberry HAT HELP

[FranzR]

Hi all, sorry for my english, I really want to thanks all the software developers for this project, FPP is the best project for light shows, thank you guys.
Since my interest in lights show and electronics I want make for hobby my own RPi Pixel Hat, I'm a college music teacher and I don't have interest in selling this, Is only a hobbist progect during the Christmas season.
I have one F16v3 and one F16v4 in my house and I want to add some pixels in the garden with a raspberry connected with ethernet.
Now, where I can start? On github there's a file about EEPROM and saw other user in this forum that already made one of this but I don't know where I can find all the info. for example what GPIO I need to use or a schematic for the hat pcb.
I have read all about new DPIpixels post on License Keys.
Thank you for the support.