When you first buy it just follow the instructions. No need to wash it but you do need to throw it in the dryer to activate it. Just make sure you put it into some sort of air tight bag or container once it's done that way it won't start absorbing scent/odors.

As for washing them, I use Robinson's detergent made specifically for cleaning carbon clothing. Scent Blocker and Scent Away also make similar products.