Thanks for asking.
You can use Header and Footer plugin to add Facebook Pixel code.
Here is a tutorial that you can use to get started with Header and Footer plugin.
In case you don't want to use Plugin, please use the solution mentioned in following thread. Please note that before making any code changes, we suggest you to install and setup Child theme:
You can download child theme from following source:
Please use following documentation to install and setup child theme:
Please note that the plugin name I have shared is not a official Themeco advice. It's just a personal input that I have shared with you to help you get started. 3rd party plugins may cause some issues and we won't be able to provide support in that scenario.