1. You start out next to your ship in front of a tunnel. Follow this tunnel until you enter the courtyard. 2. Enemies will start shooting at you. 2 of them are hard to reach at this point, so go straight for the building. Enter the left door. Inside the building, turn to the left (turning to the right only leads to the right door and a locked door to a later part of the level) 4. Press the switch in this plus-shaped room. Enemies will ambush you from all sides. Kill them and progress onwards.