Hi Lillian,
I am an independent advisor and will try to assist you with this.
You can forget the networks through 'manage known networks' option.
Select Start , then type settings. Select Settings > Network & internet > Wi-Fi. On the Wi-Fi settings screen, select Manage known networks, and click on forget next to the networks that you want to remove.
There is another option of 'show available networks'. This will show any wifi network in laptop's range of detection and you can not remove the networks from here as they just show any networks that are available for connectivity.
Hope this helps!