Cut a piece of wood to slide into the backpack so that the backpack doesnt form a bump agaisnt your back. The wood will keep the backpack flat against your back when the pack is presurized.Put the hydration pack in the backpack and feed the drinking and pump tubes through the designated slots on the back pack.I added a cable tie to the pump tube to keep it secure.Fill the hydration pack with anything you want and screw the cap on tight, connect the tubing together and zip up the back pack.Squeeze the trigger on the pump and it should fill up the pack, pressurizing it. This pressure will force the liquid out the drinking tube when the spigot is opened.Remember to regulate the pressure with the pressure regulator so the hydration chmamber does not burst.