From Skype for Business (Lync) Windows Store app, you can’t change Skype for Business (Lync) alert settings such as who can contact you while your presence status is set to Do Not Disturb. You must use Lync 2013 for the desktop to customize alerts and notifications to suit your work style. The changes you make will apply to all your Skype for Business (Lync) products.
Important: Whatever you do, don’t turn off Windows 8 notifications for Skype for Business (Lync) Windows Store app. If they are turned off, you won’t see incoming IM invitations and call requests. Instead, these invitations will display as missed IMs and calls.