You get automatic access to the innate fleet channel just by joining the fleet.
most of the TrekBBS communication happens on a channel called TrekBBS Subspace Com
to join, do this:
Right click on any Chat Tab in the chat window to bring up the Chat Configuration Window. Click on the Channels Tab and enter the name of the channel you wish to join (or create) in the Join/Create window. Then click Join. Alternatively, you can type "/channel_join ChannelName" where ChannelName is the channel.
The maximum number of channels you may be subscribed to is twenty.