Back to the Fireteam where you'll again take control over Locke and blast your way to save Meridian Station to find Governor Sloan. Make Sure you don't miss out the cutscene before this Mission to avoid out of sync battle.
After the Cutscene is over you are inside the elevator which will take you to the root to the Meridian Station. Outside the elevator take a right and head straight towards the Meridian Station. On your way, you'll encounter dozens of Prometheans trying to takeover the base. Locate and stop them from overruling the base. Make sure you use the chain guns in the same area.
After Defeating the Prometheans, head right to the top of the nearby building, continue moving until you come across the security room. Again use the Spartan charge to get inside the terminal. Once the gate is open select your Warthog, let your teammate hop in and let's drive the way in. Keep driving to the next gate and let your mate take down the enemies on the way. Once you defeat all the enemies the next door will open.
Head towards the marked checkpoints and watch out for the Prometheans driving the Warthogs soo be careful. Drive until you find the next gate(Gate 9) where Governor Sloan is waiting for us. But before the gate opens you need to finish of bunch of enemies along with two Gauss turrets.
Once they are down the Sloan will let us in and thank us for saving them from the Enemy soldiers. A cutscene will start and end of Mission 3: Glassed.