I submerge it in water, then squeeze/wring it out so it's still damp but not sopping wet. Then I put it in the warm hide, around the warm hide, (since that side dries out faster), some in a tiny water dish that stays moist to keep humidity up, and then some more on the other side. As far as how much to buy, it depends on the size of your tank and the ambient humidity. As someone else stated already, if it's in the hide your hygrometer may indicate the tank is drier than it actually is.