Question

If you have 2 forces acting downwwould you do? Add? Subtract?

Answer 1

If they are acting in the same direction like two people pushing a cart what do you think?

Answer 2

think of it this way, forces are vectors. so their direction matters. their magnitude matters. if two forces are pointing down then their direction is down. you have to be specific as to what these forces are acting on.
remember the definition of a force: In physics, a force is any interaction which tends to change the motion of an object. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described by intuitive concepts such as a push or a pull. -Wiki
its so easy when you think of them as vectors :)