curve driven pattern

When I try to pattern a shape along a 3d curve with "curve driven pattern" I'm prompted to enter a face normal:

"Please select the face on which the curve, specified in the first direction lies". What does that mean?

Solidworks is astonishingly remarkable lacking in user interface, especially regarding help and feedback on functions. Maybe it's not allowed (or you need to use a different function) to use a curve in 3d – but why then is it eligable in the frist place? SW should implement the idea to check input values. I'am completely annoyed. I payed for this f#ing product and I don't even get a manual.