How to Forget a Saved Wi-Fi Network on Windows 10
Launch the Settings app by opening your Start menu and clicking “Settings.” Select “Network & Internet” in the Settings window.
Select the “Wi-Fi” category and scroll down to the bottom of the list. Click the “Manage Wi-Fi settings” link.
Scroll down to the bottom of the Manage Wi-Fi Settings link, scrolling past all the options about Microsoft’s Wi-Fi Sense feature. This is the same settings pane that allows you to choose whether or not to share a network with your Facebook, Outlook.com, and Skype contacts.
You’ll see a “Manage known networks” list at the option here. It contains a list of every Wi-Fi network you’ve connected to. To forget a network, click it and click “Forget.”
The next time you connect to a network, you’ll be asked for its passphrase and Windows will set it up from scratch.