1) Google your router and model number and find the default settings IP address.
2) If its password protected, try the generic ones (admin, password, etc) if you didnt write down the password.
3) Go to Security or Privacy settings and use 64-bit incoding to protect your signal. For some reason, 128-bit doesnt always work with all computers/laptops.
If all else fails, call the helpline for your router and they will walk you through the settings and they can change your passwords if you forgot em