As a channel manager you have the option to add/remove users to the channel and to promote the 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 which users you would like to add to the channel. You may only add to your channel existing member of the community. If you wish to add someone who is not already part of the community, please contact an administrator.
To remove a member simply click on the cogwheel 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.