How do I mount a wall mirror for a dining area?

Dies it have a frame? Just hang it like a picture. If unframed you'll need to buy a mirror j channel for bottom and top. Screws into wall and hold the mirror. You can also add mirror mastic on back. Do not use non mirror glue, it could eat thru the silvering on back.

Hi Nancy. A large mirror in your dining room will reflect light and help to make the room seem bigger. You should secure your mirror by using the studs inside the wall to hang it from. Begin by drilling pilot holes. Use a drill bit that is slightly smaller than the screw. Using this method will insure that the mirror will never fall. It is way better than using a wall anchor for something this heavy. Good luck Nancy.

Does the back of the mirror have any hardware already?

If not, and if the mirror is heavy, then I would recommend purchasing a french cleat which is a sturdy mounting system suitable for heavy artwork and mirrors.

https://www.wikihow.life/Hang-a-Heavy-Mirror

You can screw directly in the wall.

Add a wire side to side then put nails into the studs and hang the wire. Use poster putty to hold into place once it's level.