On your right is a SHOTGUN.
Pick it up and walk through the doorway on the left. Go north up the stairs onto the platform to find a box with AMMUNITION. Take it and in your inventory put the ammo in the shotgun. Walk south twice to return to the entrance hall.
Walk north on the right side of the room to find a large metal door. Use the door to go through but beware: the enemy is behind it. Use your loaded shotgun to kill him before he kills you. Your first obstacle is taken. But outside…..
Game source: A copy of the game was found here on the internet.