Serious question about University of California?

Your school will send out information on all of this when the time to take each test comes. In tenth grade, I'm pretty sure that the only major test you have to take would be the PSAT, and you will be able to sign up for them at your school. When the time comes for the others, you will get information sent home on how to sign up for them ONLINE. But you still have a while until you need to worry about it.