If you are permitted, you can select the fields to display by clicking Choose Fields in the Summary Options drop-down:
This will give you an alphabetical list of fields available for display (left hand column) and those already selected (right hand column). In the left hand column, highlight the field you wish to add. In the right hand column, you can specify where in the view you want it to sit by highlighting the field that you wish the new field to sit next to. Use the > and < chevrons to move the fields to and from the list of those available and those selected.
Clicking OK will save your field selection, and then your new field will be included in the view:
You get to the equivalent field selection box in the SupportDesk Windows interface using the View section in the Home ribbon tab or Choose Fields on the Options menu: