This guide describes the requirements and limitations for the Groups API that allow you to read and create Facebook Group data on behalf of group members.
Groups API uses a 2 tiered API access level system, Standard level and Advanced level. Standard level access will only allow you to get data for users that have a role on your app, while Advanced level access will allow you to get data from all users in the group that the app is installed in.
Advanced level access to the API requires App Review. To gain access, include the following features and permissions with your submission.
publish_to_groups(required if your app will publish data to the group on the member's behalf)
groups_access_member_info(required if you want access to group member public info. — see limitations below)
Group admins can locate and install your app as described in the Help Center, How do I add an app.