How to Forget a Network on your MAC

1.  Choose Apple menu  > System Preferences, then click Network
2.  Select Wi-Fi in the list on the left

3.  Click the Advanced button.
4.  The Wi-Fi pane shows a Preferred Networks list.  Select the Wi-Fi network that you want your Mac to forget.

5.  Click the remove button (–) beneath the list.  If you're asked to confirm, click Remove.
6.  Click OK
7.  Click Apply