The first mission, Over Freeport City Bank, is an introduction level. Your performance on this mission affects where you start on the next map, but is otherwise simple that you might not notice any difference.
When you gain control of Blade, you will need to shoot two people on the roof. You need to aim downward to get the two targets in view when they're at the edge. They'll quickly move behind cover, which won't last long in the turret.
The helicopter will turn around, where you face the bank. The secondary objective, minimizing Hardcorp casualties, is complete by shooting at the cracked arch on the front of the bank. This prevents the enemies inside from destroying any more vehicles.
If you want a rooftop landing, aim at and shoot the three rocket turrets on the roof. Some can be quickly killed by aiming at an explosive behind them. The rooftop landing is closer to a key required to access the security area.
If you prefer approaching at ground level, simply wait for the helicopter to take enough hits. This brings you closer to Mancini, although you will still need to fight through a few rooms for a key.