The way I did it was
Tools
1. Small stubby phillips screw driver.
2. Handfull of small self tappers.
1. Cut the raised tabs off with a fresh Stanley blade.
2. Find the middle of the splitter and screw a self tapper smack in the middle so the tip just pokes through, then leaving an even gap to each side work your way out screwing self tappers, as before screw till the tips poke through.
3. Find the middle of the bumper and put a mark where it is, then screw the middle screw in splitter to it. Then offer up the next bit to screw, hold it in place with your free hand and then screw it in with the other. (Repeat till end)
4. Using the Stanley knife cut off the bits that stick out into the wheel arch. (If you make a clean enough cut, you could glue the end back on if you trim it down)
5. Stand back and admire your work.