Make sure you download the correct armeabi-v7a or universal version for Android 5.1, and enable "Unknown sources" before installing. Also, this is just the Store app – if your core Play Services are too old, some features might not work.
A screen will pop up detailing the permissions the app requires. Tap at the bottom right corner. Make sure you download the correct armeabi-v7a or
When updating core system files like the Play Store through external packages, keeping your data secure is paramount: Make sure you download the correct armeabi-v7a or
Tap the completed download notification (e.g., com.android.vending_xx.x.xx.apk ). Make sure you download the correct armeabi-v7a or
The Play Store relies heavily on Google Play Services (often requiring version 9.4.52 or higher for older Android versions).