You put your food in it and hang it from a location they cant get to...
Actually, the nice thing about the canister is that you don't have to hang it. I've started hiking in a few parks where hanging food is mandatory because of black bear populations. Hanging food is a pain, and it's not always foolproof. So I bought the small bear canister. You just put food and any toiletries with a scent in there, and then you place it at a distance from your camp. Bears can't get in it. They might bat it around a bit, but unless they grow thumbs and have a coin or screwdriver in their pockets, the food stays safe. Some parks out west now require bear canisters, in part because the bears have become accustomed to them and know that it's futile to try and harvest food from them.
Here's another throw-up bag photo. Getting ready for a hunting trip, and here's what's in my deer hunting fanny pack. I'll probably add my phone, a walkie talkie (I'll be hunting with a buddy), and a camera to the pack.
L to R: K&M match case (that compass has kept me on the right side of the tree more times than I can count), key to my stand cable lock, Gerber saw with bone blade, bright eyes tacks, flashlight, grunt call, Denning hunting knife, rattle bag, ammo pouch, head lamp.