Shared Access gives admins and users options for posting with or without certain credentials. There are a few scenarios that can apply for shared network access:
If you aren't the owner (maybe you're a marketing team member, ad agency, intern, etc.) of a users' Facebook page, you are still able to post on behalf of that user, view that networks' activities, and export archive report for that network if they share their network access.
If an admin is the only owner/admin on a Facebook page and shares access to the account with the user, then the user can post also. If they don't share access, then user does not get to post or view the page in the platform
To share access, navigate to Social Networks> Accounts> choose the account you want to share account access with >click the arrow button circled in red below