Shreyas Kalrao :
You cant change IP address -_-
Of course you can. What you can't (or at least shouldn't) change is the WAN IP address, which is set by your ISP. The LAN address is whatever you choose it to be.
The manual states the default IP address for this router is 192.168.0.1. For the initial setup, I recommend you to connect it only to a notebook/desktop through cable. Set the notebook NIC's IP to something like 192.168.0.2, then login to the router at http://192.168.0.1. Change the router's IP address in the main page, as stated in page 31 of the manual:
http://www.dlink.com/-/media/Consumer_Products/DIR/DIR%20600/Manual/DIR_600_B_2_Manual_EN_UK.pdf
Set the notebook's IP to something in the same range and you should be able to connect to it again.