Measure across the edge you want to trim out. Find and mark the middle.
Apply tile mastic over the back of the first bullnose tile, using a notched tiling trowel.
Set the tile to the wall, next to the area being bordered, on one side of the mark at the middle. Position the tile so the finished (``soft'') edge is facing away from the area that's being bordered. Set spacers between the other edge of the tile and the area.
Hang the rest of the tiles along the edge in the same manner, working out from the middle toward the ends in both directions. Line up the finished edges to form the border. Cut the tiles at the ends to fit, as necessary, using a tile cutter.
Allow the mastic to dry for 12 hours. Remove the spacers.
Grout the tiles using a grout float, by scraping over the faces of the tiles and pressing the grout into the spaces between. Wipe off the excess grout with a dampened sponge.