[**Complete other side quests first before start this quest to rank up your character and purchase upgrades. All stores will be locked and inaccessible once you've completed this quest.] Now get to the roof and go through the door.
You are now in the middle of the alien spaceship, naked and unarmed. Keep going forward until you find a door.
Press the RMB to defend yourself and kill the Zin.
Keep going and eliminate Zin troops you come across on the way. Fight across the bridge that leads you to a platform.
Stay on defend position untill a cutscene triggers.
Use the WASD key for direction, and the mouse to lean forward or sideways. [**DO NOT use WASD key instead, use your mouse to control the ship. Believe me, it's a lot easier.]
Sometimes you need to press SPACEBAR to move faster. Keep flying ahead, avoiding obstacles, and shoot enemies down.
When you reach the closing door, stay at the widest spot -- the bottom. You'll fly outside shortly.