You either cut a hole, or when you pump the ball, put the tube in and then when it is almost out, leave it there. It should make a hissing sound and you should be able to feel some air blowing.
you...
Simply... the valve is a one way valve that lets in air one way but does not let air out. It it basically a hole with a flap on the inside. The flap closes when pressure is pushing out but opens when...