USB Stick is designed to make file storage on your iOS device as easy as possible, but due to a handful of limitations it falls short of that goal, though not so much that the app cannot be of use. Primarily useful for moving photos to and from your device via iTunes or Dropbox, USB Stick can be used for other types of files, as well, though most file transfers will require a handful of additional steps.
When you load USB Stick for the first time you can connect locally through iTunes to move files to or from the app. The folder support option is locked in the free version, but there is also Dropbox support, which you can enable from a second menu. You can also load photos from your photo library and then move them to a folder of your choice or into Dropbox or iTunes, but these steps are never quite clear. You'll have to figure out exactly what the app requires to get these steps done on your own due to a lack of directions.
USB Stick offers a minimal menu, strict trial limitations, and at-times confusing options to choose from, so it can present more obstacles than a tool designed to streamline file management should. Ultimately, it works as intended, but there are easier ways to move your files.