To create user group Click "Users"->"User groups" ->"New group" and fill the form.
Group name = This is group name that will be displayed in assignment page;
Group description = this is just description
Default for new registered users : if you select this box ,then all new registered users will be in this group .
Start date : this is the Start date of group .
Study Years : This will be displayed in assignment pages . If you don't want to use study years just enter "0" . If you enter start date 2011 and study years 8 , then in 2015 the users in this group will be in 4th course .
Show in assignments page : For admins you can uncheck this checkbox and this group will not be shown in assignments page