I found it on the USNA Admissions website in thirty seconds.
Steps for admission: United States Citizens living abroad.
How you apply depends on why you're living in Canada, but yes, any American citizen who meets the basic requirements (age, not married, no dependents) can apply for admission. Are your folks still American citizens? If so, of where are they residents? If they're, say, Florida residents and just living/working in Canada, you'd apply to the Florida congressional delegation. If either of them are veterans, you an apply for a Presidential nomination. Otherwise, you can only apply for a Vice Presidential nomination.
You don't get a "letter of recommendation" from your Congressman. You're trying to get a Congressional
nomination. That's Congressman X saying to USNA, "I officially nominate Stellardark to the Academy from my district". Then it's up to the Academy whether to actually offer you an appointment. If you get a Primary Nomination and are competitive for admission (good grades, athletics, extra-curriculars, etc), you'll usually be offered an appointment.
Don't get the idea that that means you have to know your congressperson. You don't. Most of the time, the Congressperson won't even know who the hell you are - it's all handled by staffers.
