You would be surprised by the amount of people searching for “ftp dreambox” words in the box at the top of this page. Hey, that’s it, just to “finally make you happy”:
1) Download an FTP client (FileZila is recommended)
2) Create a new connection profile using your Dreambox address (192.168.x.x for example), root as username and dreambox as password (some firmware have no default password set for this, so just leave it empty)
3) Connect!
Easy, isn’t it?