The user who adds the page to Lightful must be either an Editor or an Admin on the Facebook page. This gives you the correct permission to add your Facebook Page to Lightful.
Follow these steps to check what type of access you have to the Facebook page:
Click Settings at the top of your Page.
Click Page Roles in the left column.
From here, you can see your role listed below your name.
Ensure that the role listed below your name is an Admin or an Editor. If you do not have these roles under your name contact the admin of your Facebook page to either:
Sign into Lightful with their Facebook details to grant access to the Facebook page
Grant you Admin or Editor access to the Facebook page