When you upload files, you can do it individually file by file or en masse with bulk upload.
To upload, you can either drag and drop a file or write that file to your Box account.
To drag and drop, it is usually best to first move the item file to your desktop so you can grab it, and then drag it to your open browser with the Box.com webpage open. Then you can simply drop it into a folder that you have previously created.
To write the file to your box account, click the "Upload" button at the top of the screen. It will then either give you the choice of uploading individual files, or folders of multiple files. Note that you can upload more than one file at once through the files option. That being said, you will have to choose which files to upload, rather than having the ease of simply selecting one folder and uploading its entire contents at one time.
This is what the files upload option looks like:
You can select however many files you want, and it allows you to pick through a folder if you don't want to upload everything in it.
This is what the folders option looks like:
You choose one folder and it automatically uploads everything in that folder. This option works best for large batches of materials that you'd like to keep together in your Box account.