Installing a FB Pixel
HOW: Put a bit of code in the backend of your website
Show ads to people who have visited your website in the past (also known as retargeting), and
track conversions with your Facebook ads.
Tutorial: https://clairepells.com/how-to-install-the-facebook-pixel-wordpress/ (outdated in some areas)
http://facebook.com/ads/manager – then Events Manager:
Facebook Pixel: Track Website Activities – Add the Facebook pixel to your website to track ad conversions, improve audience targeting and maximize your return on advertising spend. See the actions people take after seeing your ads and create audiences to reach people similar to your best customers.

- choose a partner: WP
- download/install plugin through the WP dashboard of your site
Use Server-Side API
This topic is deferred for now – see link below for details:
https://developers.facebook.com/docs/marketing-api/server-side-api#server-side-api