OS X Use Notification Center
Notification Center lets you view details about your day—appointments, weather, birthdays, even a summary of what you have planned for tomorrow—and catch up on notifications you missed.
To open Notification Center, click its icon 
in the menu bar, or swipe left with two fingers from the right edge of the trackpad.
Tip: To customize or stop notifications, click the Notifications preferences icon in the bottom-right corner of Notification Center.
See your day at a glance
In Notification Center, click Today, then do any of the following.
Get details: Click an item in a widget. For example, click an item in the Weather widget to show the hourly and five-day forecasts. Or click an item in the Calendar widget to open the item in the Calendar app.
Take action: Click a widget item or its checkbox. For example, click an icon in the Social widget to post your latest news to LinkedIn, Facebook, Twitter, or Messages. Or click a reminder’s checkbox to complete it.
Customize a widget: Move the pointer over the widget, then click the Info button
that appears.
Reorder widgets: Click Edit at the bottom of Today view, then drag a widget up or down.
Add or remove widgets: Click Edit at the bottom of Today view. To add a widget, click the Add button
. To remove a widget, click the Remove button 
; the widget is moved to the list of available widgets. Get more widgets: Click Edit at the bottom of Today view, click App Store, then buy or download widgets from the App store. For more information about buying and downloading apps, see Find, buy, and download apps.
If you don’t see an account in the Social widget, choose Apple menu > System Preferences, click Extensions, click Share Menu, then select the account. Only accounts that allow posting or messaging appear in Today view.
See missed notifications
In Notification Center, click Notifications, then do any of the following.
Get details: Click a notification to see the item in the associated app. For example, click a Mail notification to see the email in Mail. When you open an item, it’s removed from Notifications view.
Remove all notifications for a day or app: Move the pointer over a day or an app in Notifications view, then click Close
.