Installing a lip/general principles
If the contour is about the same, find the center of the car, and the center of the lip, line them up and do one fastener in the middle.
Work from the middle outward to avoid wrinkles, and get a smooth look.
Plastic push-ins are at the autoparts store. Drill holes as needed.
Metal screws are at Home Depot.
For a lip that doesn't have the exact contour, get back to me, and I will elaborate on the solution.-Bob