basically, you line up the top of the lip to where the paint on the bumper ends... i started by drilling screws on the ends of the lip to the fender/wheel well and worked my way to the middle underneath the bumper... it took only about 6 screws in total... it'll fit terribly at first, but after some coaxing it'll start to look factory...

oh, and i used some basic metal screws with washers from Home Depot