@jjd6980 

If you need to set up a static IP address on your router or a public static IP you can do that by logging into the router and going to Advanced > Network > Internet, and choose the connection type Static IP. All the other boxes such as the IP, Subnet Mask, will need IP addresses entered that you should be given, typically by the ISP:

If you just need to assign your VOIP phone a static IP address, something like a 192.168.x.x address then you can reserve an IP for it so it is static. You just need to enter the MAC address of the VOIP phone, the IP will be a number outside of your DHCP pool. So while in the DHCP Server menu, look at the IP it gives out. It should be something like 192.168.0.100 to 192.168.0.199, so give the VOIP phone an IP of 192.168.0.50