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Go to the https://developers.facebook.com/apps/ and login at your Facebook developer account.
Click Add a New App button on the top right to create a new app ID. A popup will display as below
In the Facebook for developers Settings, choose Basic, click on the Add Platform button, then enter your site URL.
Click on Save changes button. You will see that there are App ID and App secret, note that you will need these to configure the module in the backend of Magento 2.
Choose Facebook Login > Settings link from the left menu section at the apps page, fill in Valid OAuth Redirect URIs with the Redirect URI obtained from Magento 2 configuration.
Then you have to make your app public to everyone. On the top bar, click on Status, a pop up as below will be displayed. Confirm to make the app public.
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