1) Choose Apps in the header navigation and select Add a New App.
2) Add App name
3) Go to "Settings -> Basic" and add "App Domain" and Click "+ Add Platform" and Click "Website" and Set "Site URL" and "Save Changes"
Note: App Domain have not http and www (Ex: joomcore.com).
5) Get App ID and App Secret
You can see video here: https://www.youtube.com/watch?v=851F-Drpt40