Hy Kirk,
thanks for your reply. I was in the IPTC Info Dialogue and there you can only tag the actual photo.
If I understand it right, I select some photos directly in the contactsheet, open the "Structured Keywords Panel", then select the Keywords and at last click on "apply collection to selected".
Is it possible (if not this will be a featurerequest for the future) to drag'n drop Keywords directly on selected photos?