Using a supported browser, or with the app installed on Android, sign in. You should see a message at the top of the screen asking you to enable push notifications. Tap the link and then tap Allow in the pop-up.
If you don't see the message at the top of the screen, visit Your Profile using the menu. From there you can enable and stop push notifications.
You can stop receiving notifications on a particular Android device or desktop browser via Your Profile. Tap the Stop notifications button to disable them for the device/browser.
You can enabled them again at any time by tapping the Enable button.
Trouble enabling or stopping notifications?
If you're unable to enable or stop notifications via your profile, you might need to adjust the notification permissions for your device, or the app itself.