See the help in SW and use those examples (Make those examples) then place them into a drawing. You will get the option to use Flat-Pattern. That is the only difference between a part and Sheet metal part in a drawing.
Just don't panic when the flat pattern comes into your drawing rotated. Seems to be problem with Solidworks. Just right-clk on the view and use Zoom/Pan/Rotate to rotate the view.
As for the cone, try creating it as a thin-wall revove feature. The trick is to not revolve the full 360 deg. Stop a little short to leave a seam to unfold from. then select one edge of the seam and Insert Bends.