Connect a computer to a wired connection on the router. Point your browser at click here That should take you to the admin interface of the router. If that doesn't work, check the documentation that came with your router --- it will give you the correct aaa.bbb.ccc.ddd IP address.
do a hard reset on the router and start over. "Hard reset" is not just a power cycle... there is usually reset button on the bottom or somewhere that requires a stylus (pen, paperclip, etc.) to push it... you usually have to hold it in for 30 seconds or more to cause the hard reset. This will take your router back to factory default settings for everything.