For information about what customers are spending time doing in the apps, log into your Google Analytics account. From this account, you should be able to see separate profiles for both Android and iOS and will be able to find out stats such as actively used app versions, real-time user interactions and popular devices.
You can access app download reports directly from the respective app store accounts too:
- Log into the Google Play Developer Console at https://play.google.com/apps/publish/
- Select your app
- Select 'Statistics' from the left menu
- Log into iTunes Connect using your Apple ID at https://itunesconnect.apple.com/
- Select 'App Analytics'
- Select your app from the list