Enter email and device ID on Options page
How to get Email and Device ID:
install Device ID app, it will show you your Device ID and Gmail.
For example: if it shows android-1234567890abcdef , then your device ID is 1234567890abcdef
Do not type in random email or device ID, it won't work, if you logged out your phone or reflash your phone with custom ROM you might need to relogin APK Downloader again
That's it. You can now start using APK Downloader.
After logging in, you can navigate to any Google Play App page, and wait for a few seconds for icon to appear and click the APK Downloader icon in the Address bar to download the .apk to your desktop!