Discovery Live allows to input 3 components of force vector in x, y and z direction. It is through these inputs that the direction of applied force can be controlled.
To specify the components click on + sign near the added force
In the picture below, force is applied in z direction and the arrow direction reflects the same
If I change the components such that force is now applied in Y direction, the arrow changes direction appropriately.
I hope that answers your question.
Thanks & Regards,