7 STEPS
1. The first step is to open Dex. and click on Notifications (bell icon).
2. Here you will see the notifications that you are currently subscribed to.
If the toggle button is green, you are subscribed.
If the toggle button is white, you are not subscribed to the notification.
3. Click the toggle to turn it on.
4. or to turn it off.
5. Once the change has been made, then a notification will pop up stating the notification was updated.
6. Click the X to exit out of the notifications screen.
7. That's it. You're done.
Here's an interactive tutorial
https://www.iorad.com/player/1820200/Dex--Subscribing-and-Unsubscribing-from-Notifications-in-Dex