How do I move my assembly origin to a new position?

I'm still a bit of a novice here.  I've got well over 6 hours design into this Assembly and realized I never started my assembly at the origin.  I have designed several parts in context as well as inserted in external parts.  I would like to know how to get my origin in the correct postion.  Do I need to move all the parts or can I simply move the origin?  See pic below

SolidworksAssemblies