Upon landing, move north. You'll immediately encounter patrolling guards. Avoid them by sticking to the edges of the screen. Your first goal is to enter the building directly north of your starting position. There's a single guard patrolling the entrance. Wait for him to move away, then quickly approach the door and press 'A' to enter.
Inside the building, you'll find a few rooms. The first room contains a single guard. You can either punch him out (press 'A' when unarmed and close) or sneak past. Your immediate objective is to find the Binoculars. They are usually located in one of the lockers or a small room on the first floor. The Binoculars allow you to scout ahead by pressing 'A' when equipped, revealing enemy positions on the next screen. This is an essential item for planning your stealth approach.
After acquiring the Binoculars, proceed to the next area, always keeping an eye on enemy patrols. Remember to use your radio (Select button, Big Boss 120.75) if you need a reminder of your objective or feel lost.