Back up all databases that will be updated to the new version. If you subscribe to CDM+ SAAS or Data Hosting you can contact support to make a backup or simply rely on the nightly backup.
Click the link above to download the installer for your platform.
Follow the Installing CDM+ guide to install CDM+. This will remove previous versions of CDM+ from your computer.
Open CDM+ and update your database(s) to the current version.
Check out What's New in CDM+ 12.0.