Hey, you can get the address online from CIC official website; or if you have already applied to immigrate to Canada, you must have received an acknowledgement letter (letter of acceptance) from the office you applied and/or a letter saying that your application has been transferred to a visa office nearer to your country. If so, on the letter, you get an address of the visa office you need to use in case where you want to contact the office or where you want to send additional information.
Samilegama,
Good luck!