The Debian Linux Distribution has its own system of download mirrors. Since as administrator you are not so much concerned to download the packages, but rather to select the packages you want to install, only the following command is what you have to remember:
apt-get install dict-freedict-la1-la2
Here la1 and la2 are the 3-letter language codes from ISO 639-2 of the languages of the dictionary you require. Of course, that language combination has to be available in FreeDict.
You can find out what FreeDict packages are available in Debian by visiting
The FreeDict pages in the Debian Bug Tracking System might also be of interest.
This page might as well be of interest: Debian FreeDict Packages team.