Learn more about getting started with Facebook Pixel here.
Adding your Facebook Pixel will allow you to track traffic to your Social Link Pages in your Facebook Business account.
To get your Facebook pixel, follow the above instructions to generate one.
Then go to the "settings" tab and copy your pixel id:
Once you've copied your Facebook Pixel Id, go to your Social Link Pages builder, open the "design and options" panel, and paste your pixel id into the Facebook pixel id input.