Moreover, the buttons and sticks you are used to, are faithfully mapped and, since you are used to their feedback and layout from the countless hours you've spent before your favorite console, the learning curve is rather flat.
1. On Sony DualShock 4, press and hold the PS button below, and the Share button to the left of the touchpad together. On BT-enabled Xbox controller, hold the Xbox button in the middle to turn it on, and then press the Connect button at the top of the pad to enter pairing mode (the logo will start blinking)
2. Go to Settings > Bluetooth > My devices on your iPhone or iPad, and tap the respective listing to pair your game controller with your iOS gear
3. That's it, on the Xbox pad the logo will stop blinking, while on the DualShock 4 a red strip will light up at the top of the touchpad indicating a successful pairing. Now go kill'em all!