As a channel manager you have the option to add/remove users to the channel and to promote channel members to managers.
To add a new member, go to the Manage Members tab in the Channel Management panel.
Click on Add members and then search for the users you'd like to add to the channel. You can only add existing members of the community to your channel existing. If you want to add someone who is not already part of the community, please contact the community administrator.
To remove a member simply click on the settings icon as below:
From here you also have the option to change a user's role to Manager. This change however can only be reverted by the community administrator.