Detailed mission walkthrough:
You will have to wait for the train to reach a new station. Here's where you'll be granted with your first task.
New mission objective: Find a way to the upper levels of the Munitions Plant
Head on to your left. After that, you will have to find a small door (screen). Once you're inside a new corridor, wait for some new orders to be displayed on your screen.
New mission objective: Advance through the rocket defense system
You will have to be extremely careful here, because this corridor is filled with traps. You'll be dealing with rocket launchers, so you can't make any major mistakes. Otherwise you would have ended up dead. You've got two choices here. If you don't want to have any major problems, you should consider destroying the turrets. You will also be required to dodge rockets in slow-motion.
If you don't want to spend too much time here, you may consider risking your life by running towards nearby control panels, much like the one displayed on the screen. I have to warn you, though. You will be avoiding a lot of rockets along the way, even if you're using slow-motion. As a result, I would recommend destroying all turrets, instead of trying to disable them, even if it means staying here longer.
Either way, you will have to reach an opposite end of this corridor safely. Save your game there and proceed to the nearest door. There are two guards here. The first one is very easy to kill, because he's standing in front of you (screen). The other one is to your left. You won't have to use powerful weapons to kill them, because they aren't heavily equipped.
Head on to a new door, however don't exit this room, because the area is not safe. Instead, familiarize yourself with your new task.
New mission objective: Access the upper control rooms and activate the wind turbine
Lean out carefully and kill a few soldiers. Some of them will be standing nearby, so they'll have to die first. There's going to be at least 3-4 of them. Once they're gone, go back to the previous room and save your game.
This area is being guarded by two enemy snipers. They are standing to the left and to the right (screen) of the exit. Obviously you must combine slow-motion with a crossbow or a sniper rifle in order to get rid of them. Make sure that they have been killed. If you're having some difficulties finding them, be on a look out for red laser beams. You should also know that some of the "standard" soldiers may advance towards your position. Kill them as well.
You will probably have to kill one more soldier. He will be standing to your right, near the elevator. Eliminate him from a larger distance. Proceed to your left. You might want to consider entering a new room here, however you would only find a crate with a crossbow inside. Go back to the stairs (screen) and turn right. Save your game here.