It's very simple, when you are in Dolores's office, go to the table and activate a red button, a false wall will open, take the key and go towards the elevator, when the elevator arrives, there is a passage well above you . In the next part, you need to be careful, there is a trap that needs to be deactivated as soon as you disable it, grab the crank inside the drawer and enter the hole in the floor near the trap. At that point, you should be at the top of the safe. just open all the padlocks and you will win