How do I make a patch iron on?

You can use a product called Stitch Witchery which is available in notions departments of craft or sewing stores. Directions come on the package, but it’s basically just ironing with a layer of the product between two pieces of fabric. You can also buy iron on patches which have glue on the back, but they are generic colors—they won’t match exactly. With Stitch Witchery you can make a scrap of fabric into a matching iron on patch.