Semi inflate the tube so that it takes shape, try to put on one side of the tyre first starting with the valve, then push that side into the center of the rim, using a decent tyre lever hook the other side of the tyre onto the rim, as you get to the last part of the tyre let the air out of the tube and pinch the tyre into the center of the rim again and hook the final part of the tyre onto the rim. Good Luck!