How to reset dlink router?

Press and hold the reset button of the dlink router for atleast 30 seconds and then release it.

(make sure your router is turned ON while resetting the router)

and after that wait for the lights to come up and when all the lights will lit up ,it means router is ready to setup now.

or

if you have access to the web interface of the dlink router.

then go to tools and select system option

and under the system option ,select factory defaults.

and then it will reset the router.

Step 1. Open the Web browser and type 192.168.0.1 or 192.168.1.1 into the Address bar at the top of the window; press Enter to open the D-Link Web interface. If the IP address doesn't work, somebody may have configured the router and changed the address.
Step 2. Type the username and password into the Username and Password fields and then click Log In or Submit to open the Web interface page. If you changed the default username and password and can't remember them, you may need to reset the router by using the reset button.
Step 3. Select the Tools tab at the top of the interface and then select the System option from the left pane. The tab position and option names may vary between models and even firmware revisions. Consult the manual that came with the device to find more information about the Web interface.
Step 4. Click the Restore All Settings to the Factory Defaults button and then confirm your action