Games : How do I testfor if a player is standing on a certain block on a certain coordinates

So I'm pretty new to testfor still and I would like to know how to create a commandblock system that would detect when they are standing on a yellow wool block on the coordinates 400 4 600 (for example) does anyone know how to setup this redstone suystem, and also be specific about how I set the redstone system up, so for example show me a picture on how the setup of it would look like.