This is how i done it.
open Settings -> Network & internet -> Wifi
Click/tap on Wi-Fi in the left pane, click/tap on the connected wireless network name (ex: Brink)
Click/tap on Wi-Fi in the left pane, and click/tap on the Manage known networks link under Wi-Fi on the right side.
Click/tap on the wireless network name (ex: Brink-Router2) you want to manage, click/tap on Properties
Turn on or off to Set as metered connection for this Wi-Fi network
You can now can close Settings if you like.