Without Play Store
If you for some reason cannot use Play Store it's possible to install the free version of the app directly using the APK file.
Every version is available from https://android.roysolberg.com/datacounter/releases/
as seen in the frame below.
Generally a more recent version number is better. But if you are running an older Android version (1.5-5.1) you want to download version 2.3.2