Under Files you keep everything that belongs to your work. You create the folder structure yourself.
Create a folder
Click New and choose Folder, or right-click in the list. Give the folder a name. Folders can go inside folders; drag a folder to move it.
Upload files
Drag files from your computer into the list, or click New and choose Upload. You can pick several files at once. Large files take a moment; you'll see the progress at the bottom.
Move, rename, delete
Drag a file to another folder to move it. Renaming and deleting are in the right-click menu. Anything you delete goes to the bin, where you can restore it.
Storage
At the bottom of the sidebar you can see how much storage you use. If you reach your limit, free up space (the bin counts too) or choose a larger plan.