Trying to extend my wifi

Ok first you restart your modem by powering it down and then back up. Connect your wndr3400 to the modem by connecting the ethernet cable to the WAN (Internet port) on the back of the wndr3400 which is colored YELLOW. On the bottom of your router there should be the wifi name and the password. If you never changed it use that to log into the wifi. Once you're connected to the wifi type 192.168.1.1 on your cell phone or http://routerlogin.net. It will ask you for user and password. The user will be admin and the password will be password unless you had previously changed them. If you're not able to do any of these steps just do a hard reset to that router by pressing the reset button for 30 seconds while powered on and it will go to defaults. You can run the setup wizard to detect the internet from the modem once you're in and change the wifi name or password if you want. Make sure the password algorythym is set to WPA2 AES to get maximum speeds.