Applying forces in an angle/ specific direction

Hello everyone! 

I am trying to apply a force in a specific direction for a project I am doing.

The scenario i have is: suspension rods transferring load onto a flat body.  The rods are position at an angle to both vertical and horizontal plane which results in a force required to be applied in a very complex direction. Do I need a reference geometry to be imported (lets say the surface of the rod and its position relative to the plane i am trying to apply force to) or maybe i need to a 'guide line' onto which to force is to be created. I  I am looking for some help on how this can be done.

Thanks in advance.