As with MOST bodykit pieces, this should be installed by a professional - but I've posted these photos for anyone who is curious as to how/where the actual install points are located - these photos should answer most of your questions
my celica rear bumper attachments are different than yours. i didn't have those attachment points on the upper part of the rear bumper. my attachment points went all around the top of the bumper, and were hidden behind the plastics inside the car. there were no points that were visible from the outside.