Run your application and copy Key Hashes from console and fill it into form.
10. Click on App Details option on the sidebar and add the relevant information about the app.
11. Turn on the App Center Platform settings for your mobile/web site
to list your app in app center.
12. Add icons, images, and videos as specified in the settings page. The images and icons need to be of the mentioned size and resolution.
After the app registration is done you need to upload the APK for your app and submit it for review to Facebook team. It takes 5 business days for the team to approve your app.you can start using the App ID generated to implement Facebook functionality in your app before approval as well.