and follow the video to know how to setup your Firebase project and connect it with your app
Make sure that the package name of the app identical to the one in the firebase and the apk is in release mode if sms verification doesn't work double check package name and sha1 fingerprint
Make sure that the apk is in release mode not debug mode
The used comment (replace it with your data) :
keytool -list -v -keystore "c:\users\your_user_name\.android\key" -alias yourkeyalias -storepass android -keypass android