Using Bluetooth pairing the RK61 can easily be paired with consoles like Playstation and Xbox. On your PS4 menu, go to 'Settings', then 'Devices' and then select 'Bluetooth Devices'. If you don't see the RK61 keyboard listed as one of the device to pair with then on the keyboard hold down Function (FN) and P keys together till the P key starts flashing and then release.
The RK61 keyboard should then show up on the list of devices on the PS4 as 'RK-Bluetooth-Keyboard', you might have to scroll down towards the bottom of the list to find it. Then select it and the PS/4 will ask you 'Do you want to register this Bluetooth Device', and then you just select yes and your PS/4 and RK61 keyboard should be paired.