To change your notification settings:

Access Account Settings by clicking the gear icon in the top right corner of the dashboard.
On the left side, click Notifications under User Preferences.
You will see the list of available notification types on the resulting Notifications page. Next to each type, you can select if you wish to receive the notification in-app (in the UI) and/or by email.
The first row of checkboxes under the In-App and Email column titles allows all notifications of that type to be turned off/on in bulk.
If you select neither choice, you will not receive the relevant notification. By default, all in-app notifications will turned ON and all email notifications turned OFF.