The process you found is to control access to Verizon's WiFi hot-spots. If you're trying to change the password on your home WiFi network, that's different. Just because Google showed you the hot-spot password management process first doesn't mean its what you want. Google is not omniscient.
Try this link, which appears further down in the search results for "change verizon wifi password:"
If you don't know your router's administrator password, it is most likely printed on it's label. Don't be confused when the router shows multiple dots for each character you type in the password field. It's a security feature.
Enjoy!