Important:

Until April 5, 2023, passengers entering or transiting through Canada whose first point of embarkation is China (People's Rep.), Hong Kong (SAR of China) or Macau (SAR of China) must have.

• • • A negative COVID-19 antigen, NAAT or PCR test result performed no later than two (2) days before departure from the first point of embarkation; or
    • A positive COVID-19 test result performed more than ten (10) days but less than 90 days before departure of the first point of embarkation.
    • This does not apply to passengers under two (2) years of age.

Vaccination and health: not required.

You need an eTa (Electronic Travel Authorization). You can stay in Canada for up to 6 months. 
Eta visa exceptions:

1. Foreigners with official Canadian documents.
2. Travelers with a valid Canadian visa.
3. Travellers with valid status in Canada (e.g. visitor, student or worker) who are re-entering Canada after visiting only the United States or St. Pierre and Miquelon.
4. Foreigners in the following situations:

• French citizens living in St. Pierre and Miquelon and flying directly to Canada from St. Pierre and Miquelon.
• Foreign nationals who are passengers bound for or departing from the United States on a flight that stops in Canada for refueling only, and have the necessary documents to enter the United States, or have been lawfully admitted to the United States have been lawfully admitted to the United States.
• Aliens who are passengers on a flight that makes an unscheduled stopover in Canada.
• Foreign nationals transiting through a Canadian airport under the Visa Free Transit Program or China Transit.                                                        

Applying for eTA:

1) Documentation to present:

1. A valid passport, a valid email address and an acceptable credit card to pay the $7 CAD fee (non-refundable): 1. Have your passport and credit or debit card ready and read the help document: https://www.canada.ca/content/dam/ircc/migration/ircc/english/pdf/eta/s…
2. Use the online form to make your application. The form cannot be saved, so have your information prepared.
3. Pay $7 CAD for your eTA after completing the form.
4. You will receive an email regarding your eTA application. Most applications are approved within minutes.
5. You may need to submit documents before your application can be approved. http://bit.ly/2JjKUlL

2) Apply:

You should have carefully read the help guide in your preferred language, then start filling out your online application which you will find here.

More information here