It sounds to me like Tina is trying to put a replacement glass/backing plate into the existing door mirror housing.
The prongs on the back of the mirror have to press onto the tabs/into the accepters on the power mirror tilting assembly (or vice versa, not sure how Toyo mounts theirs)
They can be tough, but put on a glove, press your palm onto the mirror glass and push flat on, the assembly can take it. Support the other side of the mirror with your other hand for posterity. I've had to replace a few...