Install the Tiles
Spread thinset on your backer board, keeping your trowel at a 45-degree angle to create substantial grooves (Image 1).
Again, mix a batch of thin-set mortar to a peanut-butter consistency. Let it set for several minutes after stirring. With the notched trowel, spread a slightly thicker layer of thinset than that between the plywood and backer board on top of the backer board.
Using drywall screws and an electric drill, countersink screws every 8 to 10 inches.
Set your tiles carefully onto the thinset and "wiggle" them into place (Image 2).
As you proceed with setting the tiles in the thinset, use a level to check your tiles regularly for accurate, level positioning (Image 3).
Make sure to use spacers between the tiles to preserve a straight grout line (Image 4). As with the laying out, use thin spacers to minimize the width of the grout lines (Image 5).