Upgrades are not restricted in Helix Plan, any license allows the server to be upgraded at all times.
In general, you cannot downgrade a Helix Plan server.
1. Run the installer.
The installer will shut down the Helix Plan server service, take a backup using Helix 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.