People who aren’t full SCCA members need to fill out a weekend membership form. You can find them at the reg table if you’re registering on-site or fill one out online if you prereg.
The cost is an additional $15. The form has a number ID on the top right corner which you can use to get your $15 applied towards your full membership if you want to join SCCA. You can use up to two of them towards your full membership.