Begin by logging into your Weebly account.
Once logged in, go to your site's dashboard.
In the dashboard, locate and click on the 'Settings' section.
Within 'Settings', find and select the 'SEO' (Search Engine Optimization) option.
In the SEO settings, look for a box labeled 'Header Code'.
Paste your tracking pixel code into this box.
Make sure to save your changes after pasting the code.