Hi,
You will have to make sure that when you go to Network > Interfaces and check LAN interface you could see that protocol is set to static and your IP is set to something like 192.168.x.x (e.g 192.168.1.1). If you plan on using WiFi instead of LAN to connect to Unifi, then do the instruction above only for WAN interface.
That's all you need to do, to set your router IP address to static, but if you have something else going - please provide me with the topology of what are you trying to achieve.
EB.