Upgrades are not restricted in P4 Plan, any license allows the server to be upgraded at all times.
In general, you cannot downgrade a P4 Plan server.
1. Run the installer.
The installer will shut down the P4 Plan server service, take a backup using P4 Plan's built-in backup system, run the upgrade process and then start the service again automatically.
2. Install the server in the same directory path as the existing server
3. Check the server log for any problems after the installation has finished. See Configuring logging options and email notifications.