How do I change the size of the game client when in window mode?

To change the window size from the Updater: 

1. Login to the Fallen Earth Updater.
2. Click on Options located at the bottom left of the launcher.
3. Under Video Settings tab, click on the Resolution drop-down menu and select your window size.
4. When finished click on "Save", then launch the client with your new settings. 

To adjust window size while in-game: 

1. Press Esc on your keyboard which will bring up the Menu, or click on the Menu button.
2. Click "Options".
3. Click on the Graphics tab.
4. From the Resolution drop-down menu choose your desired window size. 
5. Click on OK, and your client will restart to apply the new resolution.