I have made several posts in regards to this operation. Remove the four retainer bolts that hold the Impact absorbers to the frame. Then remove the two bolts that hold the tail pipe hanger on the passenger side. Then you can pull the bumper back and let it hang on the shocks. You do not have to remove the bumper completely. You can disconnect the taillights and the fibre- optic lines. Open the trunk and get the bracket retainers 77deville mentions.
You will find you may have to trim the edges of the mounting frames to get them to fit inside the ABS plastic replacements. Careful, go slow and do not try to force them or you will crack the plastic. Depending on how fussy you are, you will find making them line up can be a pain.
When ready, reconnect the taillight connections, slid the impact absorbers back into the frame tubes, and bolt them down. Now you may find that the bumper sets back too far. You may have to remove some shims between the Impact absorber flanges and bumper. It helps to have two bumper jacks to make this adjustment. The bumper is heavy, and difficult to work with.