In order to add a Facebook pixel code or Google Analytics or similarly any other codes in your landing page, you will have to add it manually.
Here are step by step instructions for you to do it.
Step 1 – Find the landing page template ID by opening the screenshot in new window.
Step 2 – Edit index.php file of the template.
Now you know what template you are using, open that template folder and edit the index.php file inside it. In this example it is tpl_02. So the path would be
wp-landing-pages/llp_tpl/tpl_02/index.php
Step 3 – Enter your Google Analytics or Facebook Pixel code between the </footer and </body> closing tags.
Step 4 – Save the file and upload to your site via FTP.