Here is the msdn documentation on the listview object and the listviewItem object.
http://msdn.microsoft.com/en-us/library/system.windows.forms.listview.aspx
http://msdn.microsoft.com/en-us/library/system.windows.forms.listviewitem.aspx
I would highly recommend that you at least take the time to skim the documentation on any objects you use from the .net framework. While the documentation can be pretty poor at some times it is still invaluable especially when you run into situations like this.
But as James Atkinson said it's simply a matter of adding subitems to a listviewitem like so:
ListViewItem i = new ListViewItem("column1");
i.SubItems.Add("column2");
i.SubItems.Add("column3");