I get an error after drawing a rectangle and try to use Contour Flange. The error "The sketch profile for this feature must be open." is intermittent. I am also new in ST8. Thanks.
For the closed profile, you can only transform into a Tab. The countour flange needs to be non-closed, to be able to receive other sheetmetal features.
Or you can make it as a solid part with thin wall, and then, convert that into a sheetmetal part, ripping off the edges first.
(I'm in ST7, but I think the logic is still the same)