Once you've landed at the Emporia assist Elizabeth in opening a floodgate for the airship and also listen to what the Lutece siblings have to say. You'll receive a card with instructions from Robert after a while. Move the piano so that you'll be able to continue your journey.
Search the luggage belonging to the escaping citizens of Columbia and then use the stairs leading to Port Prosperity. You're going to be attacked by a large group of the Vox in the square in front of the station and a grenadier will be among them. Use nearby tears to your advantage, summoning med kits or a Mosquito.
Once you've killed all hostile units inspect a luggage cart found in front of the station. You'll find some silver and a lockpick here.
When you're ready to move on with your current mission ask Elizabeth to open the station's door (she won't need any lockpicks). Enter the building and turn left to find another locked door. This time you will have to use three lockpicks. If you've managed to unlock the door, then you will be allowed to collect a new weapon (Heater) and an Infusion #19 located inside a steel basin at the end of the corridor.
Return to the area near the entrance to the station and open a tear located above the main door. Use the maintenance hook you've summoned to get to the left scaffolding. You can find Gear #25 and a lockpick on the scaffolding (it's inside a new basin).
You must now proceed to the corridor leading to the gondola station. You'll encounter several Vox along the way, but they won't be a serious threat. A proper fight will begin after arriving at the station. Notice new tears in this area. The first tear is located to the right of the exit and it summons a Mechanized Patriot and the second tear is located at the platform and it summons a turret. In both cases opening a portal will make the upcoming battle much easier for you. Wait for the gondola to arrive and get ready to start attacking a new squad of Vox accompanied by a Motorized Patriot of their own.
Once the battle has ended take your time to explore the platform. There's a Vantage point #31 - Telescope to the right of the gondola.
Approach the opened cabin of the gondola and find a new lockpick near the door. The cabin itself contains salts and a Hand Cannon.
The second cabin of the gondola is locked, but it has a very simple lock that doesn't need any lockpicks. Once you're ready to move on to the next chapter open this cabin and start the gondola.