Welcome to JA.
It has little plastic type hooks on the back of the glass that hook into the top of the bracket on the mirror assembly and clips on the bottom of the glass that clip into the bracket. Connect the leads for the defrost if equipped hook in the top and push the bottom into the clips and thats it. If you look at the glass and the bracket on the mirror first you will better see how it goes in. It can be a little difficult to install but dont force it too hard or you can break the mirror or the bracket.