hello @ZACHKON ,
@kyL397 is correct. In the Samsung Members app on your S21, there is a banner on the main page. You click on the banner and follow the directions to enroll in the Beta program. Once enrolled, it usually takes 5-10 minutes before you're able to actually receive the software update. If you're not automatically notified, you can go into settings->software update->download and install . If the enrollment has been processed, then the Beta download will begin. It shouldn't take that long now, when the betas first roll out and EVERYONE is trying to download at the same time, it sometimes would take a while for the Beta enrollment to complete. But you should be able to download it pretty quickly now.