It depends upon the category of Canadian Immigration for which you are going to apply.
If you are applying under the category of Federal Skilled Worker then your applications must be submitted to Centralized Intake Office (CIO) in Sydney Nova Scotia.
For Family Sponsorship Category of Canadian Immigration your application should be submitted to Case Processing Center (CPC) in Vegreville. In the case of inland Canada Sponsorship submit in Alberta and for Sponsorship outside Canada the place is Ontario.
Applications for Business Category should be submitted to the Canadian Immigration Visa Office which is located in your home country or where you reside for more than one year lawfully.
Under the Provincial Nomination Program of Canadian Immigration or for Province of Quebec, your application must be submitted to the respective province where you like to reside.
There are two scenarios for Canadian Experience Class Category,
Have to submit the application in Canadian immigration Visa office in Buffalo, New York if you are residing in Canada at the time of your application submission.
If you are not residing in Canada then you have to submit to the Canadian Immigration Visa Office, which is located at where you are residing for more than one year lawfully