You can do 2 things:
(Assuming you have the movie on your PC)
1) Create a .torrent in uTorrent (or any other torrent client) of the movie with public trackers. Upload the .torrent to seedbox, seedbox will download the data.
2) Transfer your movie to seedbox via FTP (You'll get it when you buy seedbox). Make .torrent on seedbox.
Thank you.