I have already written a blog post about doing a factory reset on older iPads and iPhone (with a Home button). As the newer models do not have a Home button, the procedure has changed.

If you forget your device passcode or PIN, there is no way to get into your iPhone or iPad again. You have to do a factory reset of the device. For that, you need iTunes and a USB cable to connect your device to your PC.

Find below the steps to recover your handheld:

Important: These steps will wipe (delete) all your data and settings from your device.

1. Connect the device to a computer with a USB cable
2. Open iTunes on the computer
3. Press and release the "Volume Up" button
4. Press and release the "Volume Down" button
5. Press and hold the "Power" button until the device is in Recovery Mode
6. In iTunes, click "Restore".
7. In iTunes, click "Restore and Update".
8. If you are shown an iOS Update screen, click "Next"
9. On the License Agreement, click "Agree".
10. The device will now be updated with the latest updates and then it will be factory reset