The DHCP settings are located further down the Setup -> Basic Setup page. Select and enable the DHCP server. The Local IP address is what you want your router set to, I have listed an example. The default Subnet Mask is 255.255.255.0
Finally the DNS settings have been configured to use Google’s DNS servers rather than BT’s. You can just leave them at 0.0.0.0 for DNS 1 and 2 if you want to use BT as your default DNS lookup.