Once authorised, you will receive your FTP credentials to acces your own private directory.
Your private directory is organised like this :
This is where you'll find all your configuration files:
Use this folder to upload your own stylesheets :
This is where your own images are and called from your custom stylesheet. You may organise it as you want, create subfolders, etc.
All of your press files are located in that folder and will be linked from the 'about/press' page on your site.