How to setup a Facebook integration
First, navigate to the campaign where you'd like to connect the Facebook integration, then click "Integrations" from the menu on the left side of the screen.
Click on Facebook in the list of available integrations.
Then click Connect Account.
You will then be prompted to log in via Facebook. Ensure you accept all permissions when doing so.
From there, select the Facebook page you'd like to connect, and click "Save".
If your Facebook page is not showing in the list, click the "Connect New Account" button to connect a different Facebook account. Ensure the account you connect has admin access to the Facebook page.
If this process is not working, there may be a problem with your Facebook account permissions. Follow the steps here to troubleshoot this.