There's some silk-screen printing on the board (first pic) - a box surrounding a 2x3 grid of holes filled with solder, with XYZ printed against these. You'll need a bit of solder wick to clean the solder out of the holes/pads, then get a 2x3 0.1" pitch header, insert into the board and solder in place. Then you need a a cable form to connect into there (many choices, google Dupont connectors) - to make off the cables for the axis sensors. and run these to each of the three axis microswitches.