static IP on TD-W8960N

Enter router web portal (see gateway IP using ipconfig in windows command prompt )
Goto advanced setup
Goto Lan
Under Enable DHCP shows "Static IP Lease List", click Add.
On the "DHCP Static IP Lease" page:
Enter MAC (using format XX:XX:XX:XX:XX:XX)
Enter IP
Click save.

Note find your PC's mac using ipconfig /all in windows command prompt.