How to use:

Loosen all straps and buckles on the compression sack before trying to fit the sleeping bag in there. The sleeping bag should be stuffed into the full volume of the compression sack and then it can be tightened later.
Take hold of the end of your sleeping bag and bunch it up as you insert this into the bottom of the compression sack.
Hold onto the side of the compression sack as you feed the rest of the sleeping bag into it, little by little, bunching it up as you go.
Hold the sides of the sack and stuff the last bit of the sleeping bag into the cylinder-like sack. It will want to puff up out of the opening but hold it down as you cinch the draw cord of the opening shut.
Get a good grip on the bag by holding it between your knees or placing pressure on it on the ground and one by one, pull the compression straps tight. Make your way around to each one and tighten the same amount and then tighten all of them again, and again until they cannot be tightened anymore.