Add Apps into App Management

There are 2 main streams of apps deployment

via EMM

These apps are listed in Google Play store and need to be approved for deployment.  The advantage of installing EMM approved app is supporting silent installation and update.

Android > Google Play > Search Apps > Approve

Check if the app has been added : Android > EMM Managed App, and App > App Management

Ad Hoc 

For apps are not listed in Google Play store, they can be added into App Management as Ad Hoc.

App > App Management > + Create > AdHoc App