All members of TRMN will belong to the most important unit: the chapter. Within the navy, that chapter will likely be a vessel or space station; marines will join marine detachments; army personnel to shore installations. Civilians can join a naval chapter or be uninformed and work on a merchant ship or in Astro Control at a junction control station. Each chapter will be assigned a city of charter or port of call, representing that area to the rest of the organization and located in geographical districts. The chapter will be where you can meet other local people, connect, cosplay, play games or even raise money for a favorite charity or organization.
The links here show chapter and fleet/district locations. It will give you an excellent chance to see if there is a chapter near you!