Admission to college is a complex issue that is directly related to individual college requirements and time lines. I would ask for information on admissions at each college you are interested in attending- course requirements, school transcript, testing requirements (SAT or ACT), high school activities, and perhaps a writing sample to demonstrate your work.
Students complete the required admission procedures in the fall of the senior year and will receive a notice of admission or perhaps be put on a waiting list, or being declined admission. If you are an adult who has graduated from high school the admissions requirements may be a bit different, but overall requirements are likely to be the same or similar depending on the college.
The bottom line- make sure you know the college requirements and time lines and follow those directions carefully.