For most schools, after you submit your application to them through Common App, in anywhere from a few hours to a day or so, the college will email you a link to an “applicant portal.” Through that link, you can make an account with the portal, and through it they’ll update you on your application status (whether or not you’ve been accepted) and ask you for things like financial aid forms. It’s important that once you get that email, you sign up immediately so you can see if there’s anything you need to give them before you know if you’re accepted or not. Also, after acceptances have started rolling out, continue to check them! You never know what each school is going to throw at you. 

There are also some schools, like UNCSA, that conduct all their applications through an applicant portal. Typically they’re really well laid-out, so you don’t need too much guidance on how to navigate your way through. Just make sure to check each school’s “apply now” section on their website to see how they work their applications.