Ok, i found all the holes for the screws and bolts, for the front, rear and bottom of the sides, but inside the dooropening, it looks like i have to drill new holes.
How did you guys do it?

I used self tapping screws

I was thinking about the same, but there is made two holes in the skirt for screws, but on the car there is a 12mm(1/2 inch) hole where one of the screws is going, what did you do there