Pull up on the suction cup with firm, constant pressure to create a slight gap between the front panel and rear case.

Insert the flat end of a spudger into the gap.

The watertight adhesive holding the display in place is very strong; creating this initial gap takes a significant amount of force. If you're having a hard time opening a gap, rock the screen up and down to weaken the adhesive until you can fit a spudger inside.

While pulling up on the suction cup, twist the spudger to widen the opening between the screen and rear case.