The form is called Form IMM 5476E. You can find the form here www.cic.gc.ca/english/pdf/kits/forms/imm5476e.pdf
You can also refer to this link for more details http://www.immigration.ca/en/immigration-manuals/202-home/immigration-manuals/electronic-application-permanent-residence/1354-the-use-of-a-representative-form-imm-5476.html