A picture is worth a thousand words. http://www.teufert.net/partbook/67-76/7-i.pdf click on the rectangle with the 2 side to side arrows at the top to make full size and scroll down to rear bumper illustration. 68 topless gave good advice the only thing I would add is to push down on the bumper while tightening the center brackets first and then pull up on side bumper ends to make as straight as possible while tightening the side brackets. The reason for all this is because the holes are purposely made large for alignment and if you just install and tighten the corners of your bumper ends will usually end up at an extreme down angle and look like shite.