Unless the Business Manager Admin hasn't customised lead access in Business Manager Settings, Facebook Ad Account admins who are Admins in Zoho Social can set up lead ads. That is, it is necessary that you are the Ad Account Admin and a Portal /Brand Admin in Zoho Social to set up this integration.
Please note that if lead access has been recently granted to only a few apps, the lead information will be pushed to only those apps you've explicitly granted permission. Business Manager Admins will have to grant Zoho Social the permission to pull leads from Facebook.