Hi, with the bumper tuck it is a very scary experience (was that my 2 kids in the morning) Any way.
1st you drill a hole in each of the bumper shocks. Make sure that you wear old cloths and goggles, because the fluid in the shocks is under pressure.
2nd You push in on the bumper. So times this is easy to do and they bumper slides right in. Other times you need to find a nice tree to slowly push the car against. (or wall, big women, that kind of thing) At times the shocks will go in and out. If this happens you need to put a screw into the shocks to fix them into place.
3rd you clean up.
With all that said this does make your bumpers kind of worthless. I have been in a few small accidents over the years with e28s and it is a good thing to have working bumpers.