Enter https://developers.facebook.com/apps/ in the address bar, or click the following link.
https://developers.facebook.com/apps/
Click 「Create New App」.
New App appears in a small window. Enter "App Display Name" and "App Namespace" (*"App Namespace" may be left blank). Check the agreement box, and click [Continue].
Get past security check.
Your App ID is numbers that appears in the App ID line.
Enter your shop URL in the Website box.