Use a hammer and pry bar to take off the existing floor molding. Remove it carefully if you want to re-install the same molding at the end. Clean the floor, and let it dry completely.
Roll out your foam underlayment, starting alongside the longest wall in the room and cutting it to fit at the end with a utility knife. Lay the strips of underlayment side by side, taping the seams together with long strips of underlayment tape. Don't attach the underlayment to the floor or the walls.
Lay your first pieces of St. James flooring along the longest walls, with the grooved side facing the wall. Snap them together end to end. Put 3/8-inch shims between the edge of the floorboards and the wall, to create an "expansion gap'' that will allow expansion of the wood with climate changes. Cut the flooring pieces at the ends on a miter saw to fit.
Snap the next course onto the first, with the tongue-and-groove system on the edges of the boards. The seams of the St. James flooring will form a groove when they are locked together; this is normal.
Continue laying new courses, snapping the boards together and cutting them at the side walls as needed. Make sure to stagger the ends of the boards from row to row, so they don't line up. Cut the final course of boards length-wise on your table saw, so they leave a 3/8 inch gap at the wall.
Remove the wood shims. Re-install your floor molding, using a trim nail gun. The molding will cover up the gaps between the edges of the flooring and walls.