First of all, my sample program is here.

Prerequisites

You've installed Processing on your PC/Mac.
Also please get a SVG file to show.

How to

At first, you have to prepare PShape object.
After that, call the loadShape method.

PShape some_kind_of_shape;
some_kind_of_shape = loadShape("Some_Kind_of_Shape.svg");

Actually, I defined PShape variable as static in my sample code for simplicity.

After you've prepared the object properly, just calling shape method in draw method and you can see your svg.

void draw() {
  background(255);
  shape(some_kind_of_shape, position_x, position_y, shape_width, shape_height);
}