[Brant Bowen]

In order to create a new sketch, I'm pretty sure it has to be a flat surface, so what you're going to want to do is create a new work plane. To do this press the workplane button and it is eaiest to choose a plane of the drawing (XY, YZ, ZX) from the orgin dropdown menu in the inventor explorer thingy. Then it should show up on the screen and you can drag it from left and right and then be able to set the offset distance from the original plane. You can create a new sketch on this plane and extrude from it.