My MacBook Pro is running Catalina but says it is up to date. How do I get big sur?

X5 wrote:

My MacBook Pro is running Catalina but says it is up to date. How do I get big sur?

Big Sur macOS 11.0.1

https://support.apple.com/macos

The general answer is that updates are available for the Major version currently installed. To get to the next major version requires an UPGRADE, and that looks like a purchase (but luckily, on sale for $0).

You generally need 50GB free disk space to install Big Sur.