Static IP address for PC using a Vodafone Technicolor Router

I have configured port forwarding on the Vodafone Technicolor router to use Remote Desktop but on occasions the IP address of the computer changes, I have tried entering LAN, Subnet, Gateway and DNS into the computers TCP/IPv4 adapter but keep getting a yellow explanation mark on the network icon.

IP: 192.168.0.50

Subnet: 255.255.255.0

Gateway: 192.168.0.1

Preferred DNS: 203.97.78.43

Alternative DNS: 203.97.78.44

Thanks for any help to rectify this