Shelf gives you a number of options when it comes to uploading content from your desktop or file server. Options include:
Uploading a single file
Performing a bulk upload of multiple files at once
Uploading a single folder (and all of the files and subfolders underneath it) - folder upload is supported by modern browsers only (e.g. Chrome, Firefox)
Uploading multiple folders at once - folder upload is supported by modern browsers only (e.g. Chrome, Firefox)
All of these actions can be completed via the upload methods described above. It should be mentioned, however, that you will need to decide if you want to upload files or folders at the outset by selecting the appropriate option, prior to selecting the content that you wish to add.