“Use Arc energy to disrupt the protective barriers barring the way to the time bridge.”
The barrier is on the far side of the area. You must make it past the second Vex Gate, up the slope and over to the barrier. There are a lot of Fallen in your way plus there are Vex defending the gate directly. Hang to the left-hand side if the Arc Energy was found more toward the entrance of this area. This affording the Runner the most protection possible. Do not outpace your Fireteam. Your melee and grenade recover quickly but you cannot use your weapons presently.
On the slope toward the barrier expect to encounter at least a Reaver Captain and more Dreg. The runner should just get past them. The fireteam should kill them off and help the runner get to the barrier.
With this barrier down, you have at least one more to go through. Once again, whoever has an Enhanced Radar can likely find the Arc Energy. Remember, the Arc Energy has a number of places it can show up. Whoever is the Runner needs to collect the Arc Energy and then start for the gate marked in the far part of the map.
Once again, try to keep to the left-hand side as the Runner. Still, keep with your fireteam and move with them. Move with the team and try to keep between them. This is important just to increase your survival chance. Runners, do not engage and just focus on getting to the gate. Remember, Fallen weapons do not track properly if you do little bunny hops. Head up the slope and over to the right.
Make your way carefully to the next portion of the area where the Gate is.
Deal with the pair of Reaver Captains that guard the gate. Runners, go past them. The rest of the Fireteam: kill the Captains. the Runner can easily make it to the barrier and deactivate it in that time. Get the barrier down and head past it.