I've never know how because I've never been shown.. but how do you pull back the foreskin on a penis? Where does it even start? To me, I don't see an extra "foreskin" I can pull back... there's just one layer of attached skin like my finger or something... Apparently you need to do it when putting on a condom, not that I'll be doing that for a while, but maybe one day... and also for cleaning smegma. Please enlighten this highly naive 18 year old on sexual matters...