Ok do I go into DHCP settings 1st and make an IP address reservation by using the Add reserve rule setting?
The Hub 3.0 already assigned an Ip address of 192.168.0.14 for the PS4. Can I just add that IP to the add reserve rule reservation? Does that make it into a Static IP address before putting it into DMZ?
To be honest you've already answered your own question.
As you've correctly said use DHCP reservation to reserve the PS4's current address
Then go to the DMZ page and set the DMZ to point to 192.168.0.14.
Finally there is a vulnerability in the PS4 which means it responds to Multicast DNS requests from outside the local network. So to stop this happening add a port forwarding rule in the Superhub to forward port 5353 UDP to an unused IP address.