It was easier on older iOS devices. It appears that now you have to set up the notifications in the settings of the phone itself, plus set them up in the Telus Home App installed on your phone. I've been finding my way through this at random intervals with my new phone, and haven't quite got it sorted yet.
EDIT: I got it working today. As described earlier, you have to set up your iPhone (Settings > Notifications > Telus Smart Home > Smart Home Notification Settings) to provide notifications for the App, then within the Telus security app, tell it to deliver notifications to your phone.