You should see a letter in your EE profile with instructions on Case-Specific Enquiry. You can send it that way.
If you are in Canada now, you may wish to read the instructions here:
http://www.cic.gc.ca/english/information/offices/canada/ottawa.asp
If you are not, you will need to find the appropriate visa office:
http://www.cic.gc.ca/english/information/offices/apply-where.asp