Rear Lower Quarter Panel Seam

[Wyattman2015]

Hi
I am looking for some direction if possible.
I have cut the rear quarter panel out and need some direction around the tail light housing.
First how do I get to the spot welds behind this plate /flange and then once I get the new rear lower quarter do I spot weld to the plate / flange when replacing ?
I don't want to cut where I shouldn't.
Please see photo

https://classicbroncos.com/forums/media/b-q-p-1-jpg.31817/

Thanks for any help.
Robert