its usually through emails, thats why its advisable for you to be checking your emails everyday especially after 3 months u got your AOR, cos medicals can come anytime in form of mail, here is a sample of medical request sent to 1 of my friends last month, a format
Dear: mohdsafiuddin
This is in reference to your application for permanent residence in Canada. In order for us to
continue the processing of your application, we require the following documents:
Ø Additional Family Info IMM5406: A separate and newly completed Additional Family
Information form (IMM5406) bearing original signatures
Ø Medical: Complete or provide proof of completion of the Immigration medical examination
Ø RPRF: Pay the Right of Permanent Residence fee