Firstly, On your Android device, ensure your Bluetooth is turned on by opening settings and heading to the Bluetooth menu. Make sure the phone is in scan mode.
Secondly, With the controller, simultaneously hold the PlayStation button and the Share button for a few seconds. The controller's light will begin blinking to let you know it's in pair mode.
Thirdly, Back on the phone, look for a device named Wireless Controller in the list of nearby Bluetooth devices. Tap that device to begin the pairing process.
Fourthly, The controller's light should stop blinking and you should get confirmation on your phone that the connection was successful.
If all goes well, you'll be connected and the controller can be used to navigate the Android UI.