1 – Click Apps and then select your app.
2 – Click the Settings button on the left side of the screen.
3 – In the Basic settings,
click the Add Platform button below the settings configuration.
4 -Select Website in the platform dialog.
5 – Enter your URL (localhost
works here).
6 – In the App Domains text input, add your domain that
matches the one in the URL.
7 – Save your settings.
Check this link for detail