I need to adjust the tickover on my volkswagon

idle speed is not adjustable, it is controlled electronicly by the ECU powering a motorised butterfly valve or throttle plate. You didnt say what the problem is. poor idling/cutting out on idle? This somtimes can be cured by cleaning the throttle body and butterfly, but this will then have to have its basic settings performed by a plug in diagnostic machine.

dealer only its a fly by wire ,be prepared for bill with a meal