I've enabled the auxiliary switches and located the connection.Check out this, if your looking for a O.E. solution, you should check behind that panel first to see if there's wiring for it to plug into, i don't have the factory bed lighting and never bothered to look for the wiring i just installed a LED strip.
https://parts.levittownfordparts.com/oem-parts/ford-cargo-lamp-n1wz13a756b
https://a.co/d/gutfVCp