Try putting a towelette over your erect penis and flexing so that you raise it up and down, you are using your pc muscle to achieve this effect.

It's the same muscle that you use to stop the flow of urine. To do kegels correctly, you must isolate this muscle and only flex this (your pc muscle) muscle. Contracting any other muscles (ie: anus etc...) will completely defeat the purpose of foing kegels.