How do I properly use VectorForces?

I was looking through the explanation of VectorForce in the api-references, but I still don't get how I am to use it. My first question is, how do I control which direction it will fly? By that I mean, do I use lookVector, or like an Orientation, and do I use that to fill in the force value? The way I see it, force is applied in different amounts on different axes, causing for the directional movement. I also don't understand where I should put VectorForce in the hierarchy system, and how I should connect attachments. I'm just moving a round ball in one specific direction, and I don't get how I'm supposed to setup the attachment. I hope I was able to clearly convey my problem and I appreciate any help.