To reset your router back to the factory default settings, use a paperclip and while the router is on, hold the paperclip into the reset hole, usually in the back or bottom of the router. Hold for 10 seconds and release. You should see LED activity. In most cases the power LED will blink orange or red, depending on the model router.
Wait about 2 minutes.
Open a web browser such as internet explorer and enter http://dlinkrouter.local. or the IP address (dlink defaults to http://192.168.0.1). Note this is not a website on the internet, it is directly on the router itself. This will erase all your settings.
Depending on your router, the setup wizard will launch or you will get a login screen. The default username is admin and leave the password box blank.
DO NOT use any of the default settings. Write down your WI-Fi network name (SSID) and password, as well as the router's password which will all be created during the setup wizard.
Make sure your network name is not something personal and remember the password is case-sensitive and can include spaces and special characters.