As usual, simply drag the SPOT XTension into your QuarkXPress folder and relaunch Quark to be able to use the SPOT XTension.
This new XTension from a lowly apprentice production may be accessed via the Utilities->Spot... menu. From inside this dialog you can change any process color to a spot color and any spot color to a process color. The XTension even reports which colors are which by displaying a dog (Spot of course) next to the spot colors in your document.
By clicking on "Spot" located at the top of the dialog box you will be presented with information about the XTension.