Follow Below Steps to Enable Internal App Sharing.
Step 1: Open Play store.
Step 2: Navigate to Setting. (Inside navigation drawer of play store)
Step 3: Enable Developer Options. (This is similar to enabling Developer Options within the Android Settings app. Tap seven times on the Play Store Version)
Step 4: Once you get the “You are now a developer!” prompt, you will see the “Internal App Sharing” option pop up on your device. Enabling Internal App Sharing will display a warning regarding the internal test nature of the apps that you can now download.