Upgrading a Revit installation involves moving from a previous release of the software to the newest release.
If desired, you can install the newest release of Revit without uninstalling the previous release. The new release and the previous release can coexist, side-by-side, without issues.
For important information about using 2 versions of the software on end-user computers and upgrading Revit projects, see Upgrade a Stand-Alone Revit Installation.
If you used deployments to install a previous release of the Revit software on target computers and you are ready to upgrade to the new release, create a new deployment for the new release. Uninstall the previous software release when you are ready to do so.