This first level may seem tricky on your first go. But with patience and a fast trigger finger, this level will become much easier.
Start off by turning to your left 90 degrees and aiming down at the security camera on the wall. Destroy it. Wait for the first guard to walk through the door then jump down off the helipad, landing behind him. Kill him, then proceed through the next metal door. Shoot the security camera up high on the wall in front of you and kill the guard who should have been alerted to your presence. Edge forward slowly, always looking to the right and shoot the next security camera (it should be just above the ramp), then plant the ECM mine on the hub as you did on Special Agent. OBJECTIVE 1 complete.
Go down the ramp to the floor with Cassandra's office - shooting the guard (who is normally on the ramp) as you go. Shoot the guards in that room (using the walls as cover if you really need to) then press the switch on the desk which opens Cassandra's office. Go in and punch her (collecting her necklace) to complete OBJECTIVE 2.
Use the wooden door next to the elevator on the right to reach the next floor. Clear all trace of human life on this floor, making sure to destroy the camera as well, to make the path safe for you and the Programmer later on. Go back through the wooden door and proceed downwards to the next floor. Again, kill all guards on this floor. Watch out for the shock trooper with duel Falcon 2 silencers, he's deadly accurate. After that head to the row of offices and wait outside the room where the Programmer is on the phone. When he steps out, LET him run away. Follow him at a fair distance away from him until he opens a locked door. Inside that room is Falcon 2 ammo and a helpful little Laptop Gun. Then take the Programmer to the floor above and follow him to the computer. After he types something in the computer, wait for him to say 'Right, I'm in.' then knock him unconscious with Pistol Whip. Bring out your data uplink and hack into the terminal to complete OBJECTIVE 3.
Then activate one of the elevators on that floor and ride it till it eventually reaches the bottom floor. On the journey down, duck in the bottom left hand corner of the elevator with your Laptop Gun so you don't attract attention. Inch slowly round, still ducking, till you see the bottom of the steps then throw your laptop gun down there. You'll have inevitably run out of CMP-150 ammo so get your Falcon 2 out and finish off any guards who make it past your Laptop Gun. When the coast is clear, pick up both the fallen ammo and your Laptop Gun and proceed to the security room which you went to on the SA difficulty. Use strafe left and right to use the wall as cover while you kill the shock troopers. Once they are all dead throw the next ECM mine on the hub to complete OBJECTIVE 4.
Head to the elevator room and use the same strafe technique to clear out this room. Go through the sliding door and open the elevator to complete OBJECTIVE 5.
