If your still able to go on your network, I'm pretty sure you're able to access the Admin site for your router, if your on Windows, you can go into start and type in "cmd.exe" then hit enter, once you do that, you type in "ipconfig", then it should tell you some information. Once that's done, you can scroll down until it says "Default Gateway (192 or 10).(168 or 10).(Number).(Number)". Go onto Google chrome, Firefox, Internet Explorer or something like that and type in the numbers with the ., like mine is 192.168.2.1. It may ask you for a password, which the Username and/or password is "admin". If you're able to get to this point, your in luck, try getting your manual or something and try pressing a factory reset button or something or try changing the SSID and password.
Else if your not able to get on your network or access the admin site, you have to do this. Go to your router, get a pen or something with a tip, then go to your router and use the pen or something else and hold down the reset button for 1 minute (Minimum) to reset your router. Then your whole network should be reset and no one can access your network without configuring it, which they can't.