Potty training....?

Ive just started getting my child comfortable with wearing "undies" and now im trying to potty train her, the thing is, is that she always tells me that she wants to go toilet after shes already been, what things could I do to encourage her to tell me before she needs to go rather than after? also id rather her go to the toilet rather than on a potty, is there anything that you could reccomend to make her feel more comfortable on the toilet? (ive already brought a kiddies seat and stool for the toilet)