property Items.SelectItem(Item as HITEM) as Boolean

Selects or unselects a specific item.

TypeDescription
Item as HITEM A long expression that indicates the item's handle that is selected or unselected.
Boolean A boolean expression that indicates the item's state. True if the item is selected, and False if the item is not selected.

Use the SelectedItem property to get the selected items. 

The following sample shows how to select the first created item: Tree1.Items.SelectItem(Tree1.Items(0)) = True