How to upgrade to Big Sur?
While Big Sur has been relased as a public beta, it's not ready for general consumption.  It's going to have issues and users are expected to know how to get around issues and at least research.  Let's face it... you're jumping into the deep end of the pool - do you know how to swim or at least did you bring your floaties?
From the Beta FAQ

Please note that since the public beta software has not yet been commercially released by Apple, it may contain errors or inaccuracies and may not function as well as commercially released software. Be sure to back up your iPhone, iPad, or iPod touch and your Mac using Time Machine before installing beta software. Since Apple TV purchases and data are stored in the cloud, there’s no need to back up your Apple TV. Install the beta software only on non-production devices that are not business critical. We strongly recommend installing on a secondary system or device, or on a secondary partition on your Mac.

I'm not saying this to discourage you, in fact, I encourage all users to try out new things because it expands their skill set.  However, I do fear for users who want to upgrade to the bleeding edge on their only computer to beta software (regardless if it's Windows, macOS, or even a *nix) without having some sort of way to escape if something goes sideways.  Ask any long time user here how many questions we each have answered where having a Time Machine backup would solve pretty much all problems...
All that said...  You can do an in place upgrade and a wipe and install . I prefer the wipe and install (via USB Installer preferably).  After you've downloaded the installer....
In-Place upgrade:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/startosinstall --agreetolicense --forcequitapps --nointeraction

Wipe &amp; Install:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/startosinstall --eraseinstall --newvolumename &quot;Macintosh HD&quot; --agreetolicense –forcequitapps --nointeraction

To create a USB installer:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/DRIVENAME --nointeraction --downloadassets