The exchange platform you have used to buy HNT tokens can be used as a storage option. Note that some traders shy away from this as it would mean their tokens would be controlled by a third party. Generally, you can use any appropriate software or hardware wallet, just keep in mind that software ones are cheaper but not as safe as the hardware ones. The traders who have a bit more experience spread their tokens out to avoid risking them all if something is to happen with one of their storage options.