Clean the area around the pinhole leak, using rubbing alcohol or water. Let it dry.
Cut a piece of the repair patching material about the size of a nickel. It's better to cut round or oval patches, rather than square ones, because the corners of square patches can lift -- eventually causing them to come off.
Cover the patch with adhesive, as well as the area around the hole. Let the adhesive become tacky or hazy.
Lay the patch directly over the pinhole on the Chillow, and gently smooth it so all parts of the patch adhere to the vinyl surface. Let it dry for at least 1 hour, or the length of time the patch manufacturer recommends.
You can also run a bead of adhesive around the patch to add extra adherence, letting it dry thoroughly before using the Chillow. Weight exerts pressure on the Chillow, which could weaken unset adhesive.