Clean the wood frame with a rag to remove all dust and dirt before adding the tile. Score cuts into the wood with a utility knife so the tile adhesive and grout adheres to the surface better.
Place tile adhesive on the back of the tile pieces. Press the tile firmly against the wood frame. Scrape up excess adhesive that seeps from around the sides with the utility knife and wipe the knife clean on the rag.
Place the grout around the tiles. Choose a colored grout that complements the tile and fits into the overall decor of the room. Wipe off any excess grout from the tiles with a rag and warm water.
Allow the grout to cure for the recommended time stated by the manufacturer. Place mirror fasteners on the back of the frame. You may have to add extra fasteners due to the added weight of the frame from the tile. Secure the mirror to the wall.