Make sure your iPhone is running iOS 13 or later
Turn on Bluetooth on your iPhone
Put the PS4 controller into pairing mode by pressing and holding the Share button and the PS button at the same time
Keep holding until the light bar starts flashing rapidly
Open Settings on your iPhone
Tap Bluetooth
Wait for Wireless Controller to appear under Other Devices
Tap Wireless Controller to pair
Wait until it moves to My Devices and shows as connected
Open a game that supports controller input
If needed, disconnect and reconnect the controller from Bluetooth settings