Most strops, made of quality leather require nothing more than an occasional rub with the palm of your unwashed hand. I say "Unwashed" because you want the natural oils from your hand. Some guys like to use strop dressings, neetsfoot oil, Ballistol, etc.
It's up to you, but it is not necessary. If you choose to do so, use very little, it's easy to go overboard. I've never done it myself to any of my strops, Maybe some of the other's will chime in....