Mark the level on your wall roughly where you want to top edge of the bullnose tile to be. Measure the span from the mark to the floor.
Measure the height of one of your wall tiles and the height of a bullnose tile. Determine how many wall tiles, plus one bullnose tile, will fit from the floor to your mark. (Remember to add 1/8 inch to the size of each tile when making your calculation to account for the grout lines.) Adjust the mark up or down to accommodate the measurements, then draw a level line across the wall at that mark.
With your tape measure, level and pencil, put a vertical line from your top mark to the floor, right in the center of the wall. At the bottom of the wall, spread tile adhesive on one side of that line with your adhesive trowel. Press your bottom row of tiles into place, working out from both sides of the vertical line. Put plastic spacers between them. Cut tiles for the two ends if needed with your wet saw. Build up from the bottom, row by row, in the same fashion, until you have tiled all but the top course.
Lay a piece of wide masking tape just above your top horizontal line. There, the bullnose will line up. When you spread your tile adhesive, let it go partly on the tape but not on the wall above the tape.
Press your bullnose into place as before, letting the curved end come right to the line. Once it is all installed, pull the tape off, which will remove the excess tile adhesive above the bullnose and prevent it from getting on the wall. Pull out all the plastic spacers and let the tiles set for a day.
Lay a clean piece of masking tape on the wall just above the bullnose. Scoop out your pre-mixed grout with a grout trowel and press it onto the wall, squeezing it into the spaces between the tiles. At the top, make sure none of the grout goes beyond the masking tape and onto the wall. Wipe down the excess grout off the tiles with a damp sponge. Let the grout set for two days, then seal it with grout sealer and a small paint brush.