Get it between the cheeks, not on the sheets!
To fill it, either pull out the plunger completely and pour the lubricant into the barrel straight from the bottle, or if your lube comes in a tub, dunk the entire assembly in the container and pull up the plunger to fill. Don't double-dip, and make sure to clean the barrel each time! The hypodermic-style construction guarantees that you won't spill a drop on your partner or on the sheets till you press down the plunger.
