Question: how do you connect your ps4 controller back to your ps4 after connecting it to your phone?
Answer: On the back of your controller, find the tiny hole next to the L2 button. ... 
Use a pin or paperclip to poke in the hole.
Push the button on the inside for a couple of seconds and then release.
Connect your DualShock 4 controller to a USB cable that is connected to your PlayStation 4.