The Drop Zone and Basket icons are next to each other on the status bar.

The Drop Zone icon is used to add files to the community. For each file you add, a new document is created with the selected file attached. To get started, you can either click the Drop Zone icon, which opens a local file selection dialog, or you can just drag a file onto the Drop Zone icon. Once you select a file, or drag a file onto the icon, you are prompted to select which document template to use to create the new document to which this file will be attached.

The Basket icon is just another way to open your basket. You can click the Basket icon, or drop existing documents onto it.