Basically, all you do is mash up like 1 or 3 aspirins with the dull end of a knife or something. Then you add some Distilled Water so it's pasty but not watery. Leave it on your face for at least 10-15 minutes, then when you wash it off gently scrub your face because it's really good for exfoliating. I have just used it for exfoliating and it does help, and it made my skin really smooth.
Aspirin is an anti-coagulant which means it stops the blood from coagulating. That is why they advise people with blood disorders not to take aspirin. Also, people that have heard conditions take this to thin their blood. I am not sure how much is absorbed through the skin, but you might ask your physician.