How to activate interpolation for matinee "set position"

I want to skip parts in my Matinee, and am using the blueprint node “Set Position” for that. At least, that’s what I’m trying to do. The docs say this about “Set Position”:

Set the position of the interpolation.

if the interpolation is not currently active, this function doesn’t send any Kismet events.

It seems that “interpolation” needs to be active, but I don’t know where to look, and how to do that. Anyone?