Drag and Drop
Drag files from your desktop to the files page in Box. Your files will be uploaded and will appear in the folder where you dropped them. Dragging and dropping entire folders is only supported in Chrome. For other browsers, use the File Browser (see below)
File Browser
Click the Upload button in the upper-right corner.
Select Files or Folders, depending on what you'd like to upload
Select the file(s) or folder you'd like to upload.
You can select multiple files for upload by holding the Command or Control key (Mac or Windows, respectively) while selecting files. However, you can only select one folder at a time for upload.
Click Open or Upload
You can upload via email, to learn how click here.