Gas and Oil Home Heating Furnaces - adding vents to duct work in the basement

I want to add a vent to an unheated room in my basement. The room is 5'9" x 7'x 7'h with a window and door. It is next to the furnace and has an 8" diameter heat vent running through the ceiling that delivers heat to the kitchen above. I want to tap into this vent and heat the little room. I would like to use the smallest vent possible and would also like to know if I should creat some kind of air return system (like venting the cold air back into the furnace room). Do you have instructions available to do this?

Yoy can buy an 8 tee inch,with installed damper.Slice your 8 inch existing duct.install tee,sheet metal screw it into place.You can adjust the built in damper to what ever you desire.PDF

Ok but I need a finished look. The room to be heated has a 1/2" drywall painted ceiling. I want to attach a wall register to the ductwork extension. How can I attach it so that it does not hit me in the head. In fact I'm sitting right under the spot where the register will be.