Athletic recruiting can start very early. Some start freshman year of HS or even earlier. Many athletic recruits begin in earnest the summer after sophomore year. Walk ons at not given any sort of support through admissions. If you looking to leverage your athletic ability for help with admissions at a highly rejective school, you’re far too late in the process to do so. Unless you happen to be a superstar.
From your other thread, I know you are low income and need financial aid so I’m also going to note that D3 schools and Ivy League schools do not give athletic scholarships.