You will need to configure/setup Facebook API page under your Facebook account.
Following are the steps:
Step1: You will need to open this link with your Facebook account.
Step 2: Then, click on add a new app.
Step 3: Choose website from options.
Step 4: Enter the name of website then click on create of Facebook app Id for it.
Step 5: A pop-up will appear. On this choose category (nature of your business type) then click on create app Id.
Step 6: Click on skip Quick Start button.
This will show you AppID: 8347255666xxx like this.
And app secret key.
Step 7: Click on show button this will show you exact app secret key:
Step 8: Click on setting button on left menu. Add your app domain and contact email-id.
Step 9: Click on Add platform button. Select website option as platform.
Then, Add site url and mobile site url.
Step 10: Finally, you will need to add this AddID and app secret key in manager section under the Setting tab.