I have what I think is a simple install. I have a 150w barn light that I am installing on a vertical pole inside. From the light are 3 wires, b, w, g and I want to control the light with my new dimmer that has 2 b and the ground wire coming out of it. There is no existing switch so I want to power this from an existing outlet. I purchased 3 wire cord for the connection. How do I connect my power to the dimmer?