The first stage to the hillside map the attacking team has to set the beacon on fire while the defending team needs to protect and extinguish the beacon if a torch hits it.
Best way to do this is the go to the defending team and just crouch behind the beacon. The defending team generally throw torches from the lower floor up the beacon, so just wait until the beacon starts to light and hold the button prompt to extinguish. Note, only one person can extinguish at a team so try to be ready.