Pick the wooden door on the right; this leads back inside.
There are two guards here; one patrolling the hall and one near the exit back outside. Execute both of them while their backs are to you.
Back outside, move to the right of the dark area until you see the wooden ramp leading up. Climb the ramp to access the second floor stone balcony.
Execute the guard near the railing using a silenced weapon.
Jump onto the ledge at the end of the balcony. Follow the ledge and jump down on the tarp-covered crates.
There is a lone guard patrolling the south gate. Wait for him to turn away, then proceed to the blue door on the south wall.
Pick the lock on the blue door, but be wary of the guard patrolling the hall on the other side. Kill him and then eliminate the guard at the South Gate. Plant the explosive on the south gate to complete the objective. You return to controlling Daniels outside the gates. Wait for the explosives to blow, and then open up on the Nazis.
Silent Night
Make it through this section without alerting any guards (red cross) to earn this achievement/trophy upon exiting to the train depot.