How can I apply for any university after taking a gap year?

Answered

It's virtually the same process as applying as a freshman, and you'd be eligible for all the same programs and scholarships. The more difficult parts are coordinating with your high school to send your transcripts and teacher recommendations, since you won't be around there every day to talk with your counselor and teachers. So you should prepare for that in advance.

Colleges will want to see some information in either your essays, activities list, or additional info section (on the Common App) about what you did in your gap year, but nothing really beyond that. There isn't any grand rule that says all students must go to college right out of high schools—there are many reasons (besides a gap year) that students a year or multiple years out of high school might be applying to college. So there's nothing special you need to submit aside from your regular application.

As an additional note though, you can STILL apply to colleges as a high school senior if you want to take a gap year. Colleges will often allow students to do what's called "deferring admission" after they're accepted, where you get into a school and enroll but ask them to take a year off before beginning. That way, you can have a guaranteed spot to land after your gap year is complete, and you can go through the application process while you're still in high school, with that support system still around you for it.