You must be the administrator of a Facebook page to add it to Message.
To add a channel
- Click the dropdown menu next to All Channels.
- Select the channel you want to set up.
- Enter your credentials and grant Message access following the instructions given by the channel.
- Back in the Message dashboard, select the Facebook page you want to add in the pop-up window that appears.
- Click Done.
To manage channels
- Select the Admin icon, then the Channels tab.
- To remove a channel from your Message account, click Unlink.
- Click Unlink again on the pop-up window that appears to confirm you want to remove the page.