To move a file from one folder to another, simply follow these steps:
1) Check the box next to the file(s) you wish to move (or copy) to a new location
2) Click "Move / Copy" in the sub-menu at the top of bottom of the list of files
3) Select new destination folder
4) Click "Move" or "Copy" to complete the action
(If you choose "Move", the file will be moved to the new folder and no longer remain in the original folder. If you choose "Copy", the file will be moved to the new folder but will remain in the original folder)
Here is an annotated screen-shot:
Hope this helps but please let me know if there is anything else I can do to be of assistance and thanks for using Box!