This is done through our frontend User Panel. There is a menu item option for this. The User Panel is only accessible to logged in users, so if you want to use the functionality provided, you'll want to either push users to login prior to registering for events, or at least enable the auto user creation feature so they create a login during registration.
In Configuration, there is a User Panel tab to set various items for this feature. Then each event also has a User Panel tab where you can setup what is being offered per event.