Aiding The Outcasts Walkthrough - Fallout 3 - Operation Anchorage - Page No. 2
After you open the pod, just sit in the chair. You may wish to hit "Save" first as you'll not be getting out of the simulator again until you've completed the mission.
You'll enter the simulation flat on your back. Make note that the only health you will find is at specific health stations, while ammo will come from ammo dispensers.
Once you're on your feet, you'll enter a quick conversation with Sergeant Benjamin Montgomery, after which the quest 'Aiding The Outcasts' will be complete.