Tile cutters don't actually "cut'' the tile, but rather break it to size, which is much easier. The cutter works by scoring the surface of the tile, then snapping it at the scored line. Cutting corners is a more complicated task. An "inside'' corner is one of the four corners of a standard room, requiring a cut that makes the tile smaller on two sides to fit. An "outside'' corner is one that juts out into the room, as in the two corners of a framed chimney, requiring a corner-shaped piece to be cut out of the tile.
Take measurements of the floor and corner to determine how much has to come off each perpendicular side of the tile. Treat the measurements as two separate cuts. Mark the measurements on the tile.
Hold your straightedge along your marks on the tile and two draw two straight lines, one for each cut. The lines should run perpendicular to each other (i.e., the lines intersect each other).
Set the tile on your tile cutter with one of the marked lines positioned parallel under the blade. Run the blade across the whole tile, scoring it on the line. Snap the tile in two with the prongs of the cutter.
Turn the tile 90 degrees to line up the second line under the blade (part of the second line will be gone from the first cut). Run the blade along the remainder of the line and snap the piece in two.
Measure the dimensions you need and mark the two lines of the corner on your tile with your wax pencil and straightedge. Don't run the lines completely across the tile, but have them meet and end in a right angle on the tile face. The mark should look like a square tucked into one corner of the tile.
Use your rod saw to cut the shorter of the two lines, starting at the edge of the tile and sawing it back and forth until you reach the point where it meets the second line. Withdraw the saw, leaving the straight line cut partway into the face.
Lay the tile on your tile cutter with the uncut line positioned underneath and parallel to the blade. Run the blade along the line, starting at the end of the line that you already cut, and extending to the end of the tile. Snap the tile by setting the prongs on either side of the scored line.
Wear eye protection when using your tile cutter.