All steps to perform on your Android device:
using web-browser download NZBGet installer app nzbget-android-2.0-testing-r19-bin.apk.
NOTE: this app is only a frontend to NZBGet downloader background process, which the app installs and launches. The app isn’t updated often but it always installs the latest version of nzbget by downloading it from NZBGet download page;
NOTE: the installer app requires Android 5 or later. However to install NZBGet on older Android versions nzbget-android-1.1-bin.apk still can be used. It installs general Linux version of NZBGet daemon instead of the version built specifically for Android.
Most scripts are written in Python. Unfortunately there is no Python for Android. That means most scripts will not work. Bash scripts may work but you may need to install BusyBox from Play store. You also must configure option ScriptDir to system partition (scripts cannot be launched from sdcard). Getting post-processing scripts to cooperate is a work in progress. Please post your questions and solutions in forum topic [New Feature] Android installer.
The steps documented above will not work in Android Emulator. Installation there requires more manual work. Please see Installation on Android emulator for details.