sds speed adjustment using clearaudio strobe/disc

Just received a vpi sds speed controller and found that the supplied strobe disc does not work here in Ireland.......50HZ. I have just bought the clearaudio strobe disc and light and would appreciate a little advice on its use. There are 2 sides to the record and I have just set the speed according to the side for use with the c/audio lght source. Is this the side with the cartridge breakin groove and should I have the stylus in the groove while setting the speed. Any help, advice or tips for using this would be very welcome..............first time I've done this and don't know if I have even set the speed correctly!!!