Step 1: Build a PCB board.
When you install AgOpenGPS a folder will appear on your desktop containing a PCB folder where you will find the schematic of the PCB, a gerber file and a BOM (Bill Of Materials) file.
Upload the gerber file to a site like jlcpcb and then order your PCB(s)
Upload the BOM file to DigiKey and order those parts. Brian has a video on how to do this on his Youtube Channel
Order the extra parts that DigiKey doesn’t supply this is found on the bottom of the BOM spreadsheet.
When your you have all your stuff solder it together, hopefully one of these videos will help.