The Tours & Tickets Shop is located in the IJ hall of Central Station on the far eastern side. Show your (smartphone) ticket at the Tours & Tickets office, where you'll be guided to the bus across the street.
You can cancel up to 24 hours in advance of the experience for a full refund.
Be sure to choose the 7 hour tour as it allows you more time to explore which is essential when visiting Zaanse Schans.
Everything is fast so be prepared to go, go go.
This is the best way to explore Countryside and in very reasonable price.