Microsoft's Windows notifications appear in a panel on the right side of the screen called the Action Center. To pull up all your notifications in one place, click the Action Center icon, a small dialog-box symbol in the lower right-hand corner. As alerts about completed virus scans or new emails come in, they show up in pop-up boxes in the lower right-hand corner. You can dismiss them individually by clicking the Dismiss X button in the top-right corner. Or empty the list all at once by clicking Clear all notifications.
Beyond dismissing read notifications, you can take more control over which alerts appear and when. Open the Start menu, click the Settings button (the cog icon), and choose System followed by Notifications & actions. A batch of toggle switches will appear. These let you decide whether notifications should appear on the lock screen and, more important, enable or disable certain alerts. For example, you might choose not to receive Windows hints and tips or updates on new features.