Cant really find any good pictures of back of home theater system to see what ports are on it.
Ideal is hdmi out of PS4 to HDMI IN of receiver (with HDMI out of receiver going to HDMI port on TV).
Next best option is using optical:
Optical Out on PS4 to Optical IN on Reciever.
You will need to set Receiver to Optical Input, and you will need to set PS4 in settings to output audio via optical.