Click the link the the Advanced Search in the top right corner.
Select the appropriate filters. In this example we will attempt to create a group containing all 4th years, therefore we set the Course to Transition Year and the Course Year to 1. Set the Enrolment to Current (which means only currently enrolled TY students will be included).
Click search and then a list of students will appear that relate to your search. You must choose if you wish to make a static group or a dynamic group.
A static group is done at a point in time and any students will stay in the group until removed.
A Dynamic group outlines a set of criteria that it matches each time. So if a student meets the criteria of the group at any point in the future, they will be automatically added to the group.