The Meta Pixel ID can be included in your Landing Pages.
The option to add this information can be found both within the Builder as well as in the Dashboard.
NOTE - Follow the link to know How to create a Facebook Pixel ID
How to add Meta Pixel ID on the builder:
Navigate to Global Settings Panel > Tracking Codes.
Paste the Meta Pixel ID in the Meta Pixel ID field.
Then, save your changes and publish the page.
How to add Meta Pixel ID on the dashboard:
Navigate to the tab Settings > Tracking Codes.
Paste the Meta Pixel ID in the Meta Pixel ID field.
Then, save your changes and publish the page.