How do I add my Page into Business Manager?
When you have created your Business Manager account, the first thing you will need to do is add your Facebook Page (your business page)
If you own the page
Go to Business Settings – Pages – Add – Add a Page
If you do not own the page
If you are a freelance marketer or agency working with pages that you do not own, you should select Request Access To Page
Go to Business Settings – Pages – Add – Request Access to a Page