This small dialog is used to allow you to select a folder from the Vault virtual folder tree.
In this example the dialog is being used to select a new location when moving an existing folder. Simply browse through the folder tree until you find the location you want. Once this is selected, click OK.
Depending on the command for which this dialog is being used, you may be able to right click and choose further commands from the context menu. For example when choosing a folder for Move, you can right click and create a new sub-folder into which the selected folder could then be placed.