You must take the
SAT or the
ACT to apply to the CSU colleges.
You should take the tests during the spring of Junior year. Then retake in fall of senior year IF you have studied or learned more.
The last tests that are typically admissible are the October test dates. (some schools may take the November & December test scores - but don't rely on that!)
Apply! (apply using CSU Mentor)
Complete the
FAFSA in January (early February)
Apply for a pin number (one for you and one for your parents) now or the first week of January.