There is a time when you already started a project and then you need to import the configuration from one device you didn't created yet.
From the Expedition Dashboard, go to Devices and add the new device.
After generate the keys and import the contents go to the Projects view
Select your project and click on settings
Go to Devices
Select the firewall you want to bring to your project
Click on the Arrow that points to the Right
Click on Save
Project's Settings View
Now when you enter into your project and navigate to the Import tab you will see the device to be imported.