Facebook Ad Manager Integration Steps
Go here https://business.facebook.com/home/accounts
Click the dropdown to the profile name in the top left

Click the gear icon to the right of the business account to navigate to your business settings

Once in the business settings, click on partners. Then add a “partner to share assets with”

Type the business manager ID into the field and hit next

Select full access and click next.
Now, navigate to “pages” on the left-hand side and

Click on “Assign partners”

Select Business ID

And enter the business ID that was provided to you into the field.
Then toggle on “full control” and click next.
You’re all set!