If you are using AD then you would create the groups in AD in an area covered by Your BaseDN that you specified when configuring Openfire. Once the groups are configured in AD then you can share them via openfire. This is done by going to the Users/Groups tab, Go to groups summary, find the group and click on it then share it, and provide a scope (share with more than just members of group or not). See attached picture for a sample.
This senerio is completely different. In this case the individual is using Active Directory LDAP to populate users and groups from their Domain to the openfire server.