1. Turn on your PS4. Using a micro USB cable, connect the controller to the console and then press the PS button on the controller.
2. Once the controller light turns on, you can remove the cable and use the controller wirelessly.
You can use up to four controllers at the same time. When you press the PS button, a colour is assigned to the user.
For more details and troubleshooting please visit: https://www.playstation.com/en-au/support/hardware/ps4-dualshock-4-wireless-troubleshooting/