Training my 10 wk goldendoodle

Our loveable male goldendoodle is crate trained and will go outside when I take him on the lease. He will not let us know when he has to go and has accidents. I take him outside many times a day. Morning, after he eats and every two hours and before bed. I use treats and tell him that he is a good dog when he goes outside. How do I get him to bark at the door.

Thank you Jo-Anne