I assume you’re asking how to cross-post to Facebook automatically whenever you publish a new post on your WordPress site?
The popular Jetpack plugin does this, via their Publicize module. Once you connect your website to the social media networks you use, you can share your content across all your social accounts with a single click. When you publish a post, it will appear on all your connected accounts.
We created a video tutorial on how to activate the Publicize feature in Jetpack.
If you don’t want to install Jetpack, you can also use IFTTT to create an automation that will create a post on Facebook anytime you publish a post on your WordPress site. IFTTT is short for ‘If This Then That’. Our friends at WP Beginner have created a step-by-step tutorial on how to set up IFTTT to automatically post to Facebook from WordPress.
I hope one of these methods will work for you!