This assumes you're American.
Your school should have counselors to help you out with these steps. To make their lives easier, start looking at
where you want to go to college. You don't have to commit to one yet, and you can apply to as many schools as you want as long as you can pay the application fees, but at least start narrowing some colleges down so your counselor can help you better.
If you just want to know how the information gets to where it needs to go, you just fill out an application and send your school that, as well as your standardized test scores from the standardized test score website. A lot of schools use a common application so if you're lucky you might just have to fill out one application. You will have to write unique essays for every school that asks for them, however.
Good luck man.