How to create a sketch to match an imported object?

[RoboDLC]

I have imported a step file of a PCB that I wish to create a case for.  I want to use the step file object to locate mounting holes and connector ports.  I successfully imported the board, but I am having trouble creating the sketch.  My picture I am showing was me trying to put a sketch "on" the board which then defined my sketch plane.  But, I can't separate the sketch from the board.

So.

How do I define a plane parallel to the board on which to create the sketch?  Then how do I make the board and the sketch separate objects so that I can move them independently of the other?  Am I making this too difficult?

I am new to CAD creations and may be jumping ahead of myself here, but you don't learn anything until you need to create something, so...

I tried to use the support/learning pages but they seem to be under construction. 

Many thanks,

DLC

[etfrench]

There is no need to separate the sketch from the step file body.  Use the Project command on the Sketch menu to transfer the outline of the parts on the PCB to the sketch. Turn the visibility of the PCB or the parts when you're done with them.  Once you've transferred the outlines to the sketch, select all of them, right click, then select the Break Link command on the context menu.  You can now move the sketch geometry around. 

p.s. If you don't want to move the PCB components, then disregard the Break Link instructions. 

You will probably need sketches for the ends as well to locate the vertical cutouts.