The rar view mirror fell off. how do i put it back...

There are a few products sold at Autoparts stores. If you can find 3M brand or a brand with an activator, they seem to work best.

You need to do several things to prepare for the job. First, get some tape and outline the old mounting position from the outside of the windshield. Then clean the inside surface of the glass.

You want to separate the mounting clip from the mirror stem. Usually there is an Allen screw in the clip. Sometimes the clips have a spring underneath that needs to be pushed down to allow the mirror stem to slide off. Note the position of the clip, if the narrow end is up or down and then glue the clip to the glass in the same direction.

After the clip has had time to adhere, slide the mirror stem into the clip, tighten the Allen screw and you are done. You will have to HOLD the clip against the glass for at least 2 minutes when you are glueing it.

Or you can go to a Glass Installer and they can do it.