If you look on the back of your new kickpanels, there's usually a little dot or recessed spot that can clue you in to where screws would drill through.
As for the carpet... it's fairly straight forward. You can use some glue or adhesive to hold it along the edges near the doorsill. I would advise you to use a soldering iron to burn the holes in for the seatbelt anchor bolts. Cutting works too but it can fray.
One trick I was told was to cut off the heads of a set of screws that would normally mount the panels, screw them into the holes by hand, and then test fit the panels. When they are situated correctly, apply pressure and a little wiggle to the panel, and the sharp end of the screw will mark the backside of the panel - where you should drill your holes.