The equivalent on a Mac is System Preferences > Network and click on the "Advanced..." button at the bottom. Then select your network from the list and hit the "-"button just below the list to remove your network and then click on "OK". To get your network back, again from System Preferences > Network go to the "Network Name" and select you network from the list that appears. Alternately if you have "Show Wi-Fi status in menu bar" checked on this screen you could just go up to the wifi icon at top right in the menu bar and select your network there (under "Other Networks".
REMEMBER - before you take these steps to forget your network, make sure you know your wi-fi network password because you will need it to get back in.
Dave