Apple released iTunes 12.1 yesterday, a free update that I recommend for everyone. One of the new features of iTunes 12.1 is an all-new Notifications widget.
This new Notifications widget allows you to quickly control playback of iTunes content with play, pause and skip functionality, all right from Notifications Center! Before you can use this new feature, however, you need to enable it. It's quick and easy. Here's how.
To enable the new iTunes widget, we first need to access Notifications Center. You can do this by clicking the Notifications Center icon in the top-right corner of your screen or by swiping from leftward from the right side of your Trackpad.
Once the Notifications Center is open, we need to add the new widget. Click on the "Edit" button at the bottom to show all available widgets.
Next, we need to click on the green "+" icon next to the iTunes widget. This will add it to our list of active widgets.
Once it has been added, we can start using it!
Note that if you want to change the location of this (or any other) widget, simply go back to edit mode, and drag/drop the widget to the new location using the handle on the right side of the widget.
Bonus tip! If you want to browse Apple's extensive catalog of Notification Center widgets, enter edit mode and then click on the "App Store" link at the bottom.
You will find a ton of widgets to choose from!