Have you trial fitted it to the car already? Is it painted?
Basically remove the bolts near the wheel arches on both sides and the plus in the middle section near the hood...trial fit the bar and make sure it doesnt interfere with ur reos as u may need to remove to fit depending on the bar...then prime the bars and paint
Then refit the bolts loosely on the sides and put small amount of urethane in the middle section to hold in place then tighten bolts on the sides..
Thats for a front bar, as for skirts same procedure screws at either end need to be taken off and re-fit new skirts after priming and painting with urethane small amounts space apart and screws re-fitted on the ends...
If its a rear bar, you might need to remove rear reo once again depending on the bar, the access some of the bolts you'll need to remving lining on the boot to get to them then follow same procedure