You can download upgrades at http://duetapp.com/latest. You will need your license key to download upgrades.
- Backup your existing config file (just make a copy).
- Unzip the package and upload the new files to your server (overwriting the old files).
- Run the installation script. Your existing values will be pre-populated so this should be very quick
- If you have translated Duet, you will need to rebuild the template file. Log in, click Admin in the sidebar, then click 'Build Template File'. Your translated language file will be applied.