The app will automatically check for updates every 24 hours, but if you wish to manually check you can do so in the Settings sub-tab under the VyprVPN tab. Click the "Check for Updates" button. If you are up to date, you will see a notification at the top of the screen. If an update is available, you will be prompted to install it and presented with a change log.
If you need any further assistance, please contact support.