I'm not familiar with D-link wireless APs, but I would say that there should be a WDS configuration section in the web interface.

Note: In order to do this, both APs must have the same encryption and key and also if you are wanting a DHCP server (automatic IP distribution) the AP on the other end must be set to recive DHCP and must not be connected to any other DHCP server

(-) = Ethernet
(~) + Wireless signal

router/DHCP-----AP1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~AP2----PC