You can upload files to any folder by pressing the sky icon in the button menu.
You will be presented with the following menu:
1. "Take a photo" starts the camera and lets you take several pictures,and they will be uploaded directly into the folder.
2. "From camera" lets you add files from your phone's camera app. (Not available on Android 4.0.3)
3. "Existing files" lets you upload files from your mobile device. (Not available on iOS)
4. "Cancel" returns you to the folder and file list.