If you are an administrator or manager of a group, you can manage members from your group page: to cancel someone's group membership, go to the "Members" page and click on the "x" icon beside their name; to promote or demote someone, click on the up or down arrow beside their name. Note that you will not see these icons if you are not logged in as an administrator or manager of that group.
You can also invite anyone who is interested in the topic/project the group is working on by clicking on the "Invite Members" button in the top-right corner of the page. On the new page that appears, you can enter the names of existing members of the Canadian HSS Commons or else enter the email addresses of prospective members.

For more information, please visit Group Guidelines and Tips and What are groups?