How to update macOS after installation?

as https://dortania.github.io/OpenCore-Desktop-Guide/post-install/update.html said, I can not figure out how to update my macOS 10.15.3 to 10.15.5, probably directly update it like real macOS?

Actually I dont want the update at all, but it reminds me to update every time I open it. So the alias of the question is: how to totally turn off the update notification.

Thanks