Actually, your requirement that "I need to access to it through my own login" is what makes it "not so simple", given *nix style permissions on DH.
While there are workarounds you could experiment with, involving the creation and management of *nix style groups, they are rather complicated, non-intuitive, and a general PITA to manage for most.
That said, if you must use FTP in this way, the easiest and most secure way to do this is to set them up their own FTP use/space, and then when you need to access the files, you log-in as that user.
I prefer to accomplish this using CGI scripting. This allows the user to upload the files, but allow me to retain ownership of the files. This works especially well on DH because of DH's use of suexec, which allows CGI to tun as your user, rather than as a separate user for the webserver.
I highly recommend ffileman, which is a "free" perl-based filemanager script that is easy to install and runs well on DH. I do not recommend using PHP scripts (there are many out there) for this if you anticipate needing to upload files greater than 7MB on DH, due to the limits of DH default PHP installation.
This works very nicely when set up as a sub-domain (files.yourdomain.tld, or similar), though it can also be configured to only traverse "limited" branch of a standard directory tree. You can also set it up behind apache authentication as an alternate (or additional) security mechanism.