Create Google Plus app

1. Open https://console.developers.google.com/project
2. Create new project
3. Open APIs in left menu
4. Find and enable Google+ API
5. Open Credentials
6. Add Create New Client ID
7. Choose INSTALLED APPLICATION -> Android
8. Add your package name
9. For SHA1 key use keytool

keytool -exportcert -alias androiddebugkey -keystore path-to-debug-or-production-keystore -list -v

More detailed: https://developers.google.com/console/help/new/#installedapplications