Level and mount the shower pan by driving screws through flange and into the wall framing using the screws provided with your shower pan.
Measure the distance from the shower pan edge, the horizontal part right below the flange, and the top of the shower wall. Transfer this measurement to the drywall. Score and snap the drywall to this measurement with a razor and drywall ruler.
Place the drywall sheet on the wall framing so the bottom edge does not touch the flange. Installing a gap between the drywall and the shower pan prevents cracking. Screw the drywall to the wall frames with the drywall screws and a power screwdriver.
Repeat the last step, cutting drywall to fit your shower wall frames. After installing drywall on the entire wall, tape all of the drywall seams with fiberglass tape, spread joint compound over the tape with a scraper and let dry until the compound turns white. Cover the gap with quick-set compound and mesh tape.