Material alignment with Torch starting point

What is the best way to align the material on the CNC table, with the starting point of the torch? So if I have a square piece of metal on the CNC table and I have designed a CAD file to cut a circle directly in the center of it…what is the best way to line up the torch with the metal plate so that when the program runs…it actually cuts the circle directly in the middle of the square piece of metal?