Thank you so much for your reply.

Actually I have added CAD in the currency list.

However, when I add the client, the country of the client's billing address is preset to "Hong Kong" and cannot be changed to other country.

I finally managed to talked to my account manager for Hong Kong region and she confirmed that I cannot add a Canadian client from Hong Kong.  What I could do is to set up another profile in Canada in order to serve my Canadian clients.