Taking over after a dj with usb connection

Hi, I haven't played in a club In years and I'm playing soon..I just like to know when taking over from a dj in a club, if he is using a USB which is linked, do I just put my USB in the player without a USB and hit USB to select my first track? This won't knock off the djs last track will it ? Sorry for the silly question, just oit of practice and don't want to mess it up. Thank.you