I normally start a new component in the component editor. If there is a "similar" component, I start there. Many times, the component is the same as an existing one, but the pattern is different. I save the component in my user component library, giving it a new name. I draw a new pattern or modify an existing one. I then save it in my user pattern library, then add it to the component previously created.
Once that is done, you can then attach the 3D drawing to the new pattern you have, correcting it's size and orientation before you save the pattern again.
