from http://products.wdc.com/library/UM/ENG/4779-705142.pdf
Updating an App
Use the following steps to update an app that you’ve added to your My Cloud device.
- On the Navigation bar, click Apps to display the Apps screen.
- If there is an update for one of the apps you’ve added to your device, an Updates available link appears at the top-right area of the screen.
- Click the Updates Available link to display the Updates Available screen.
- Select the app you’d like to update from the list and click Update.
- If you’d like to view the details of the update, click Details.
- Click Back to return to the Update screen.
I’ve also found this additional guide from within the Plex Forum on how to manually update. When doing so keep in mind that deleting/disabling Plex from within your control center will also remove the app data etc.:
