Temp sender Help ASAP (in progress)

I have an electrical water temp gauge from autometer. It has ground ignition and sender wires coming from it. My question is where is the temp sender on the motor. I see one by the top radiator hose and one by the bottom. which one do I use?

The top one has wire colors as follows 1 red and 1 green/black and the bottom one has 1 green and 1 black. I'm confused and this is my first time hooking up a temp gauge. Please help quick!!!