As a group admin you can create and manage channels for the group in the settings tab.
Create new channel
Click on the 'Add new channel' button and give the channel a name and describe the purpose of the channel. Any spaces in your channel name will automatically be changed to a '-'.
Group members access the new channel in the channels drop-down menu. Clicking the 'Default' checkbox will make this channel the first in the channels drop-down menu.
Edit and archive channels
By clicking on the 'Edit' button, you can change the channel name or topic, set the channel as the default and archive the channel. Archiving removes the channel from the channels drop-down menu but keeps all of the posts in the channel.
Note: You can't archive the default channel. You will need to set another channel as the default before archiving.
You can reactivate a channel by clicking the 'Reactivate' button and clicking save.