I've searched, just as you must have, for a software download for your router, there seems none, I think I know why you tried downloading the firmware, but you don't need that, at least not at the moment.
Firmware is not for installing or configuring your router.
Firmware to your router is like an Operating System (windows/OSX) to your PC.
You may want to call D-LINK if you have free support left (1-year from purchase or first call)
You can configure your router through it's built in web-page setup. It's not too hard at all.
Hook the laptop up via network cable, and open your browser...
In the address bar type in 192.168.0.1
Here's
D-LINK's info with images showing most steps. Pretty good info here.
http://www.dlink.com/support/faqDetail/?prod_id=2833First step, choose whether you have cable connection or DSL connection and go from there. Good Luck