Align the door to the rocker and back side of cab/body lines.
Fender should have enough adjustment to gap based on that. You may have to split the difference in a sense between the door and the fender, then adjust the hoop.
Gap the hoop to fit as desired. Some apparently have bent the hoop with force or used a BFH. I tried those and was worried about damaging the hinges (while mounted on the truck). I will probably cut the hoop at the joint, then use a bfh to move where desired and reweld.
Once you get it pretty close mark around the hinges with a paint pen or marker so you can locate it. I wouldn't drill locator holes until you are ready for final bodywork.
Some are a lot easier than others. It just depends how close they were to start. Just my experience but wouldn't say I'm great or very experienced at it.
