You can just toss it in the washer machine. Put the DoggieBandana into a mesh laundry bag and toss it in the washing machine with other dark color clothing. The bag will prevent DoggiePatches from being rubbed off by other clothes. Use warm water. Chlorine bleach is not a good idea.
To dry, toss it into the dryer and let it tumble dry under low temperature.
You can also hand wash it. Just wash with soapy water or laundry detergent under warm water, then line dry.