DD was the age your DD is now when we really started, it was a long few months of peeing on the floor pooing in undies etc.. i then got her her own stool to stand on to get on the toilet which she loved and also made a big deal of saying to her ' show us how you go to the toilet like a big girl' ' you go to the toilet all by your self' etc etc.. worked for us, one day she just got it