You do need a bracket to screw them into.. basically you take the screw out of one of the spotlight corners that match up to the hole in the new cover. the bracket then sits over the foglight hole and you reuse the screw to bolt the bracket onto the foglight. The cover then sits over the foglight and the hole in the bottom of that matches up with the bracket. An allen key head screw then secures the cover into the bracket..

Hope that makes sense, I'm sure you can get the brackets from subaru...

Cheers

Brett