How do I log in to my router's admin page to change my Wi-Fi password?

I have a standard home broadband router and I want to change my Wi-Fi network name and password because I gave the old one to too many people.

A way to open my router's settings page in a browser and find the wireless settings.

I typed 192.168.1.1 into my browser like a guide suggested but nothing loads, and I don't know the admin username or password. I'm not sure if my router uses a different address or an app instead.