There is only one way to do it, fit rubber on glass and then intall the metal trim into the groove in rubber, you are right in saying the lip has to go in first and the lip fits in the groove all the way. Easier if you spray the rubber groove with WD 40 or similar silicone type spray, it really helps to reduce friction and lets the metal lip go in all the way!. its then a matter of working trim with your hands sort of squeezing trim and rubber in your palms and you,ll feel it seat down nice and close. Take notice of the center of the lower trim so that they are on center so that the joining clip covers each end. The angled top corners just snap on. If fitting screen yourself, i ,ve allways started pulling drawstring on lower inside edge in the center and work out to each edge, if you have help putting pressure on screen from outside and gently slapping screen with open palm of hand will help it seat. best regards bill.