FAQ: How to Add CALC's Widget to the Notification Center?
On your iOS device's home screen, swipe down from the top to pull the Notification Center and Tap the Today button at the top of the screen.
You'll see today's notification. Tap the Edit button at the very bottom.
On the list of installed apps that support widgets, tap the green '+' button next to each widget you wish to show.
If you want to remove any widget from the Notification Center, tap the red '-' button next to the widget.
You can also rearrange these widgets. Simply tap and hold the three horizontal lines on the right side of any widget and drag it up or down to the position you desire.
When you're done tweaking, tap Done at the top right.