College applications are open August - November....applications for the UCs and the CSUs are DUE no later than November 30th. Private and out of state universities may have different deadlines.
College Board, Tips for college Application: https://bigfuture.collegeboard.org/get-in/applying-101/applying-to-college-faq
Tips for applying to college: https://www.usnews.com/education/best-colleges/applying
Steps for applying to college: https://www.universitylanguage.com/guides/applying-to-college/
Financial Aid information:
Federal Student Aid: https://studentaid.ed.gov/sa/prepare-for-college/applying
Free Application for Financial Student Aid (FAFSA): https://fafsa.ed.gov/