How to generate google Play App Signing

Hello, google play will start app bundle format in August. Because I used the APK format before, I need to join Play App Signing at this time. How should I generate keys for the existing Expo program?

The following is the option to join Play App Signing, which one should I choose?

  1. Export and upload the key from Android Studio
  2. Export and upload the key from the Java keystore
  3. Export and upload the key (do not use the Java keystore)

I read the official document, but I am still very confused and don’t know how to operate it. Can you tell me about the operation process? Thank you