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MS Access: Update data from one table to another based on a choice

Help! I have a patient form where their referring doctor is chosen and that ID for the doctor is stored in a variable. When I click "Save record" I need it to copy the data form the ReferringDoctors table (name, address, etc) and copy it to the PatientDetails table in corresponding variables based on which doctor has been chosen. I can't figure it out. Help!

Using Access 2013

Re-edit: The whole idea here it that I have three separate tables - 1 for the DoctorInfo (just address data), 1 for the PatientInfo (just address data), and 1 for the PatientVisit info (why they came that day). The goal is to be able to click a button on the PatientVisit form to generate a letter in Word that includes the address from the doctor, the patient's address and the information from the patient visit.

So far, I have all the information I need stored in the three tables, but I have no clue how to grab the information to generate the letter. For example if Patient 1 is referred by Doctor A on the current visit, how do I generate a letter that has that information? I assumed I would need to copy the info from one table to another to eventually pass it to Word for it to use to generate the letter. Totally wrong?