Replacing door window

Im trying to replace the drivers side window on my 90 Gt. It has power windows. I removed the broken window and got out the metal bar that the arm slide up and down on along with the bracket that window is attached to. Now im stumped, im looking at the window and trying o align it to slide down inside the door frame but i dont see a way for it to fit. Dont want to break the window forcing it in, or doing something im not supposed to do. Any one have any tips or tricks for me?

I'm supposed to flex the door panel open as far as i could and try to finess the window in or what?

OK sounds good , the window was actually busted out so accessing the rivet shouldnt be a problem, is there only one rivet i should be looking for , also will this be taking the metal frame away from the door so i can place the glass inside?

just want to make sure im on the right page