Go to your Facebook Page
Click Settings
Click Privacy or Page Access, depending on your Page version
Set the Page visibility to Unpublished or Page unpublished if available
If using the new Pages experience, remove public access by limiting Page access and audience settings as much as possible
Turn off posting permissions for visitors
Review and restrict who can see posts, stories, and page content
Remove any public contact details you do not want visible
Delete or hide any posts you want kept private
If you want the Page fully private, consider deleting the Page instead
Save your changes