Cannot officially be done unless WD decides to add that feature to the lower end My Cloud units. The ability to add third party apps is a selling feature/point for their more expensive units.
The newer generation, v2.x single bay My Cloud does have the App tab but it is limited and apparently does not support the many third party modules the more expensive My Cloud units support.
Unofficially there may be ways to replicate such third party features by using SSH to install unofficial modules or alternate operating systems to the v4.x single bay My Cloud. Keep in mind however that due to the processor and RAM used on the single bay My Cloud’s one may have problems running certain unofficial apps/modules. Use the forum search feature (magnifying glass icon upper right) and search for [APP].
https://community.wd.com/t/repository-with-software-worked-on-v4-firmware/94532
