I had to cut those doors out of the fiberglass fuselage.
I made a template for the door and traced the outline onto the fuselage side, then cut out only the hinge line with a dremel cut off wheel, making sure it was only wide enough for the hinge to protrude through and allow the flat part of the hinge to sit flush with the inside of the fuselage skin.
Next I glued the hinge in place with Hysol 9462. After that was fully cured I added the 1/16" doubler to the inside of the door and glassed it in place with 4 ounce cloth, this makes the door much stiffer and since the cloth extends slightly past the edge of the door it also stiffened up the surrounding glass too.
I only cut out the rest of the door outline after all of this was cured and the formers had been installed.