When you register for the SAT online, there will be a section on your SAT registration form for you to enter up to four different school codes. You can fill schools in then, or you have the option to add or change schools up until nine days after you take the SAT.

To see the schools you have chosen to send your scores to and make changes if needed, log in to college board website, click "My Tests", and at the bottom of the page you will see a link titled "Requested Recipients." This is where you can update the schools.