I am assuming you mean "resilver" that is not a job for amateurs.
Hi Diane: Here are some sites that may help. It can be done, but it's dangerous and expensive. However, if you must proceed, here are the sites.
If you just want to cover the edges, because of water damage. Frame it. This is an easy peasy project. Straight cuts, with corner pieces can be bought at Home Depot. Glue right on the mirror with construction glue.