Open the cambuckle, take up the slack on the main strap until it sits comfortably right under your arm. Most of these bags are supposed to be worn high. Some users lean a bit while doing this and it's more of a challenge if you have a lot of weight in your bag because you have to fight the weight a bit, but this is true with any bag. A properly cinched bag isn't suppose to bind or squeeze you out of air. It is supposed to "hug you" around your back comfortably.