Ok I'll just get right to it. In order to rebushing the differential carrier you must remove it off the car. Put something under it because gear oil will go all over the place.
Remove the old bushings on a press. The original rubber bushing next to the poly bushings.
You must modify the poly bushings in order to press them in. As you can see there is a press fitted sleeve were the bushing goes. One side is lipped. The other side is not.
If you try to press the bushing in from the non lipped side it will shear the poly bushing and you don't want that.