Nice one chap. So does it already have pre-drilled holes on the splitter itself ?
It has four pre drilled holes which line up with four self tapping screws already in place on the car underside.
You remove those four, offer up the splitter and screw the self rappers back in.
There are another 18 pre drilled holes in the splitter which you need to use a 3mm drill to drill corresponding holes in the car underside. Then just screw in the self tapping screws.
You may wish to add some sillicant between the car and splitter as well.