How to install GApps on Banana Pi M4

Hi. I am using Banana Pi M4 and have installed Android successfully. However, this Android 8.1 does not have Google Play Store yet. I wanted to find a way to install GApps so I can use the Google Play Store but couldn’t find any detailed instructions. Also, how to boot into recovery mode with Android 8.1 on M4? Please support. Thank you so much