If you live in California, tomorrow’s the last day to register to vote. You can download the form and print and sign and mail it in here. Or you can pick up a form at a post office, or most people out there holding signs for someone will have them too. As long as it’s postmarked by tomorrow, you’ll be all set.
If you moved or changed your name, you have to re-register.
If you live somewhere else, check with your Secretary of State (for your state, not Hillary. You can google “your state” voter registration and it will come up.)