Read within your link for this para:
Get your exam before you submit your application
Are you applying to sponsor your spouse, partner or child?
A new application process for the spousal sponsorship program came into effect on December 15, 2016. Spouses, partners or dependent children can no longer do an upfront medical exam. Wait for our instructions before going for your medical exam.
This is called an upfront medical exam. To get an upfront medical exam, contact a panel physician directly.
Once your medical exam is done, the doctor will give you a document confirming that you got a medical exam. Include a copy of that document with your application.
If the doctor works with the eMedical they will give you an upfront medical notification printout.
If the doctor works with a paper system they will give you a copy of the IMM 1017B Upfront Medical Report form.
Attach that form to your application before you submit it to the visa office. If you apply online, you must upload that form before you can submit your application.
Only when you sponsor your dependants later on after becoming a PR ( spousal application), upfront medical exam is not allowed.
Otherwise primary and rest all applicants can go for upfront medical exam. I did it the same way for your information.
All of the above information is in reference to permanent residents applying to sponsor their families not for express entry applicants. Express entry applicants are required to wait for instructions.
I wanted to know about the appointment system for the medical exam and asked my panel physician and part of what he had told me was I needed a UCI or IME to make a reservation. That panel physician uses E-Medical, but each to his own.