To create ranks, click the 'Members' tab in your Admin Panel, then click 'Ranks' in the left menu. At the top you will see where you can add/edit/remove Set Ranks and towards the bottom of the page you can add/edit/remove Post Ranks. You can also assign a certain color and a 'badge' for each rank, so for example you may want to have all administrators display in the color red because they are an important person.
Set Ranks also have another nice feature. If you tick the 'Team Member' option and then specify a 'Tag', then this tag will be placed at the beginning of all the members who have this rank, which makes it easier to determine who has what rank. Ticking the 'Team Member' option will also place these members in your Roster.
To change a members rank, you will need to edit their profile. Just visit their profile and click 'Edit' at the top. All the administrator options/actions are at the bottom of the profile edit page.
You can also visit the 'Help" button on the admin panel (beside community).