To add a Facebook pixel, you have two options:
Option 1:
Go to “Settings” (at the top of the designer);
Go to “Settings” and switch to “Analytics”;
Paste “Pixel Tracking ID”;
Click Apply.
Option 2:
Go to “Settings” (at the top of the designer);
Go to “Pages” and go to “Scripts”;
Paste the Facebook pixel code into the “Before </head>” field;
Click Apply.