well not quite correct the code, you gotta write the vector either into a vector(x,y,z) or, caus you're creating at 0,0,0 the nullvector should work too, not certain though.
Oh and by the way you can only assign ACTIONS to entitys not the whole .wdl file !!
Code:

---

function create_something()
{
  ent_create("KT.mdl",vector(0,0,0),troop_act);
}

on_h = create_something;

---