You made the mistake of registering on the United States site where zip codes are five digits.

You should have registered on the Canadian site instead.
You can change your country of registration but it involves jumping through a few hoops.
It would be easier just to open a new account on the Canadian site.
You will need to use a different eMail address as eBay only allows an eMail address to be used once.
eBay Canada is here http://www.ebay.ca