The ability to add and remove administrators is in the administration panel. You may access this panel by scrolling to the bottom of any mBlogger page and click "Administrative Options". You will login using an active administrator login and password. When you have logged in you will be presented with the administration panel screen. To add or remove administrators, click either "Add an Administrator or Remove an Administrator".
To create an administrator, click on "Add an Administrator". You will be taken to a new page asking for an administrator username and administrator password. Type the values into the corresponding fields, and when complete, click on "Create Administrator".
To remove an administrator, click on "Remove an Administrator". You will be taken to a new page asking for the login name of the administrator you wish to delete. Keep in mind that this process is irreversible, and once an account is deleted it is lost until it is recreated by another administrator. Type the exact name (case is important) and click on "Remove Administrator".