I didn't understand why you said it was available and then said it wasn't due to a lack of translators.
There are two versions of the Portuguese language: a version for the Portuguese (Portugal) region and a version for Brazil.
Starting with version 0.74, the game supports the Brazilian version. There is no version for the Portuguese (Portugal) region.
Language selection is available in the game settings screen, at the very bottom.
Well, usually the game settings screen itself is enough.I don't have the opportunity to test version 0.74 right now, but it seems Deimus forgot to add support for this language to the stable version (0.74), as the translation was completed in the alpha version 0.75, which is on a different branch of the codebase. Therefore, this language will be available in the next stable version of the game (0.75), for all supported platforms. This is currently available in the beta version 0.75, which is still rough, and for many languages (CNS, FR, ES and a couple more experimental languages) it contains a partially updated translation database for new events in the game.