You can wear a fanny pack however you like! There are a number of different ways you might choose to saddle up your fanny pack, including across your waist (with the pack at the front or back) or worn as a crossbody bag.
Worn at the front of your waist can provide quick access to essentials, while a fanny pack worn at the back carries better if you choose to run with your pack. There are also fanny packs, like the Thrupack Summit Bum, designed to integrate with your backpack hipbelt.