Domestic helpers accompanying their employers to Canada do not require work permits but they do need Temporary Resident Visas (TRV) if they are nationals of countries whose citizens need visas for Canada. If that is the case the helper should complete the normal TRV application form (available on the web sites) and submit it to the visa office together with the appropriate supporting documentation listed on the web sites.
you can download the forms here:
http://www.cic.gc.ca/english/information/applications/5257.asp