When inflating smaller items use the small attachment. When using ensure to pinch the valve of the float so that air can pass through. If you are having trouble with the pump, remove the small attachment and press the blowing end up to the valve while pinching.
For GIANT floats use the larger attachment to inflate. Ensure the cap is on with the black piece pressed in (most giant floats have the black piece nozzle, if it doesn't have a black piece, simply inflate through the hole. The black piece will allow you to inflate without losing any air.
To deflate make sure the walls of the float are not restricting air flow. You can also deflate by opening all valves and pressing the air out. Please be careful with the floats as damage is subject to full replacement fee's.