Question

change into indirect speech the doctor said to the patient give up smoking

Answer 1

the answer you want to know is
the doctor adviced the patient to give up smoking

HAVE A GREAT DAY

Answer 2

The doctor said to the patient that he need to give up smoking.

Here the doctor is the spokeperson while the patient is the listener.

So, the format here will be speaker said to the listerner followed by the passive form of the dialogue statement.

In indirect speech, rather than using a commanding tone, it should be used in a form where it looks like advising or narrating in the third person view.