Take two pieces of foil, approx. 2' long and lay one on top of the other, then at the bottom, start folding the the two pieces together in about 1" folds, after about two or three folds, take the folded section and fold it in half so that the folded section appears to 1/2" in width. Then open up the two sheets at the top and lay them across your water pan with the folded seam in the middle, then you just gently push the foil down into the pan making a reservoir and secure the excess around the outside of the pan. Hope that's not too confusing. I should add that I don't add water to the reservoir, it is there only to catch drippings.