Please follow the steps below you get your Facebook App ID:
- Go to: https://developers.facebook.com/
- Click My Apps tab
- Click Create a New App button
- Fill in the form and click Create App ID button
- Go to Settings tab, add your page domain and contact email
- Click + Add Platform and select Website
- Then add your Site URL and click Save Changes
- Go to Status & Review tab
- Change button on the right to YES
- Back to Dashboard tab and copy your App ID