You need to try stretch it perpendicular to those wrinkles. Lift it up slightly, heat it and try stretch it as you put it back down (only slightly, not a lot)

Maybe heat gun? I’m not sure if it will or not. If it does poke a hole in it to make sure the air can escape

Yep! Please watch the DBrand tutorial for applying the wrap. It may not be from them, but all wraps work similarly. If you don’t want to watch it, basically you need to: -heat up the edge with a hair dryer (not too hot, just warm) -start with the entire edge lifted off the steam deck and not at all rounded over the corner -you want to slow roll your thumb over the corner and down the side. Apply pressure and pull the vinyl a bit with your thumb as it rolls. If you mess it up, more heat and retry it