Declassify Mission: Taking damage impairs sight
Turn to the right to find the declassify skull. The locust will start coming in from the door ahead so dig in and prepare to engage them. There's a ranged sentinel that you can deploy and tripwire crossbow to help you lay down some traps. Expect the enemies to burst in from the door across and from the emergence holes that will appear on the lower ground.
Go to the lower floor and engage more enemies that will appear ahead. Once cleared, go upstairs to the left (you should immediately see the COG tag skull on the wall near the stairs) then turn left towards several trays. You'll find the section's COG tag in the corner, beside the barricade.
Proceed to the next room where more enemies await. Clear the room as you see fit then head to the exit to complete the section.