Please follow the below steps in order to add a Channel:
*Only Team owners have permissions to do this*
1 - Go to the team name in the Teams list and click More options > Add Channel.
2 - Fill in the details for the new channel. For a private channel, click the drop-down under privacy and select 'Private'.
*You will be required to add members manually to private channels*
3 - The people you add to a Channel will be notified of this in Teams.