Add widgets to iPhone and iPad devices got possible since the iOS 8 and you have access to widgets from the notification center. To add widgets on iPhone 6 as well as remove widgets from notification center on iPhone 6 and other iPhone, iPad and iPod Touch devices, do as follows:
1. Open the Notification Center by dragging down the notification bar on the top.
2. Make sure the Today tab is active and then scroll all the way down
3. Tap the Edit button to enter the "Add and Remove Widgets on iPhone" panel
4. There you can find the list of already installed widgets on your iPhone.
5. Under the list of Do Not Include, the entire unused widgets are available and to add widgets on iPhone 6, you just need to tap the green plus button next to the Widget's name.
6. To reorder widgets on iPhone, simply press and hold the 3-small-line next to the Widget's name and change its position.
7. To remove widgets on iPhone, simple tap the red minus button next the Widget's name.
8. To completely delete widgets on iPhone, you have to uninstall the application comes with the widget.
9. To install widgets on iPhone, simply head to the App Store app and download widgets for your iPhone