Were is the actual opening?

my boyfriend and i are trying to go further in our relationship he is 15 and i am 13 he is not a vigin and i am he asked me to finger myself for him and i couldnt find the hole. i feel stupid abd he said that it was fine and a little bit funny but when ever i finger myself i need to uave him help my fingers get in haha. i no the general aera but he needs to help so help plz