Replacing existing wall switch
I am replacing an existing toggle switch with a new dimmer. In the existing box, there are 2 white wires maretted together and not attached to the existing switch. There are 2 black wires screwed to the top screw of the existing switch and one red wire screwed to the bottom of the existing switch. I can see a copper wire at the back of the box but the end is not accessible. The new dimmer has 2 black wires and one green. Being blonde and electrically challenged I have not idea how to hook the dimmer to the existing wires.