Remove any light switch or outlet covers in the backsplash area. Use a screwdriver to remove the screws and then grasp the edge of the switch or outlet cover and pull it off the wall.
Measure the height of the backsplash area of the wall from the top of the counter to the bottom of the upper cabinets and the width of the counter from one end to the other. Measure and record the location of any outlets or switch plates.
Cut the tile setting mat to the size and dimensions of the backsplash area that you measured in the previous step, using a utility knife. Measure and cut out any openings for switch plates or outlets.
Wash the backsplash area down with a damp rag with a drop or two of dish soap added to the rag. Wipe the area again with a clean damp rag to remove any soapy residue, then let the backsplash area dry completely.
Remove the backing paper on the tile setting mat and carefully position it in place on the backsplash wall.
Remove the clear plastic from the front side of the tile setting sheet after it is securely attached to the wall.
Apply the mosaic sheets of glass tile beginning at the bottom of the backsplash wall, flush with the countertop. Leave a 1/8-inch gap between the edges of the mosaic tile sheets, or the same gap the individual glass tiles are set at within the sheets. Use tile spacers to ensure the gaps are consistent throughout the installation.
Cut tiles to fit around switch plates and outlets with a tile wet saw or a manual tile nipper. Rent tile wet saws at rental centers or some home improvement stores; manual tile nippers are affordable and available at home improvement stores.
Apply grout to the tiles within 24 hours of setting them. Use pre-mixed grout, following the manufacturer's instructions. Put the grout on the tiles with a grout trowel and push it into the gaps by moving the grout trowel at a 45-degree angle to the tiles. Scoop up excess grout, but do not scrape over the grout lines or you may remove too much grout.
Wipe off any grout remaining on the face of the tiles immediately after you finish applying the grout. Use a damp sponge to remove the grout residue but avoid digging into the grout lines. Rinse out the sponge frequently and change the water often until no grout residue remains on the tiles.
Allow the grout to cure for at least 28 days and then seal it with a grout sealer.