How can I use the dictionary application in my language?

I want to use the Dictionary app (Applications>Office>Dictionary) bundled with Ubuntu in my own language, Portuguese (Portugal).

In the application preferences I've the option to add alternative dictionaries, but I've to get trough all sort of complicated and not user-friendly at all definitions.

In the Add Dictionary windows, I've a tab that should have the list of available dictionaries, but even after refreshing it only shows blank.

So, is there an easy way to add an alternative language (in my case, PT-pt) to the Dictionary application?

Fact: Please don't suggest alternative programas. I really want to use the default application.