If you are building your app for android select Google Android or select Apple iOS if you want to build your app for iOS.
4. After that you need to add Google Server API Key.
5. To obtain Google Server API Key, Visit the Firebase Console and sign in with your Google account.
6. Press "CREATE NEW PROJECT" or select an existing one below.
7. Enter a project name and press "CREATE PROJECT".
8. Getting your Firebase Cloud Messaging token and Sender ID
9. Copy server key And sender Id And Add it in OneSignal app and click next
Select your target SDK PhoneGap, Cordova, ionic and hit next:
10. After that Copy App ID
and add App id And Sender id (googleProjectId) in src/providers/service/config.ts file.
googleProjectId is Sender ID
11. You need to build and run your app on mobile at-least once to complete OneSignal registration . Then go back to OneSignal and click Check Subscribed User and Done.