If the fish have been handled carefully the males might still have their breeding hook on the end of the anal fin, but chances are they probably won't have after the wholesalers and shops have caught them. But generally males are slimmer than females just like Gemmy said
If you separate the males and females for a week and then put tem together they will usually breed if they are in good physical condition. Set up a 2ft or 18inch long tank. Have about 8inches of soft neutral to slightly acid water in it and a layer of Java Moss on the bottom. Introduce a pr of fish in the evening and they should breed the following morning. Then remove the adults and cover the tank with a towel to keep it dark. Check the tank each day for fry.