When you use the unit, remove the tape and empty. Fill the pot with water to within a centimetre of the brim and heat. Be careful if you've made a fry-pan with a handle from too soft wire because the pot will tip and douse your fire. When the water is hot or boiling, add soup or beverage. Your tin provides both pot and cup, but remember to let it cool down before you drink.
Scouts can construct the cook ring from any stiff wire.
A coathanger works very well. They'll need a pair of compasses for the first step - drawing a circle 10 cm in diameter on a piece of paper. Use the drawing as a template and form the wire into a ring. With pliers, bend the ends into hooks as shown, allowing a 2.5 cm overlap. Trim off the ends and pull the ring apart slightly.