How do I fit my drinks holder to the dashboard?

I bought a travel mug / flask which came with a holder, it looks like a flask holder you would fit to a bike and the rigid plastic is at a right angle so the clip part slides in to fit somewhere and then pushes down to the other side is at a right angle. The picture on the box shows the holder clipped into the air vents on the dashboard however it does not fit through as there are no grooves in the holder. Does anyone else have one of these and where did you attach it in the car?