1. Refer to this article below to set up a new Firebase account. (If you have already set up the Admin App OR User App Android / iOS, then you can skip this step. It is suggested to check it once again if all steps are completed)
Firebase Project Setup Guide – Part 1
Please note: All 3 apps – “Web App”, “User (Android & IOS) App” & “Admin app” needs to set up in the SAME FIREBASE PROJECT to get automatically linked with each other.
2. Enable “Phone” Sign-in provider for Users Login . Kindly Refer to this guide: Firebase Authentication Guide