You will get it in an EMAIL to your registered mail address. If you have been receiving emails from CIC in your inbox, no further tweaks, precautions are necessary. No need to be freaked out and check your spam multiple times a day.
The subject line will be "Ready for Visa/Pret pour Visa and will be from a sender with [at]
cic.ga.ca email address.
If you have given a Gmail email id like most people, then use this
tutorial to whitelist the cic.ga.ca domain (basically tell Gmail to allow all emails from that domain and not to identify anything from that domain as spam.)