example
x^2 = 16(y-2)
vertex will be (0,2)
to find the focal length
4a = 16
a = 4
the parabola is a normal concave up parabola
the focus is always inside the parabola. since we found out that a=4, the focus is (0,6) as you move up 4 units inside the parabola
the directrix is a line outside the parabola, so again by using a=4, the directrix will be y=-2 (moving 4 units down from the vertex)