He didn’t say in iOS notification area. He said, in the Blink app.
I can’t confirm if iOS is the same, but in Android you do the following.
Select: Gear wheel, bottom right.
Select: Manage account, top of list.
Select: Notification options, just underneath temperature Units, about halfway down.
Select: Schedule notification, quite near the bottom, by touching the description.
Adjust appropriate settings, of which there are several, or turn off completely, if that is your wish.