You need to download the game to start your own translation. Then you open the game files. To put it simply, you just take the folder named Assets and copy it to folder named: French or Portuguese, or any language. Then you put a small file names manifest.json in the same folder where the Assets folder will be. That's how you start your translation pack.

Than you translate text in two files: encounters.json and strings.properties Those files are in different folders inside Assets folder. Inside encounters.json you can only translate the dialogue windows, names of characters, everything else should be left untouched. 

Images should be taken, translated with Photoshop and putten back where they were.

But the difficult thing about translating Tales of Androgyny right now is it is being often updated. That means you will have to manually paste things you translated in older versions to the encounters.json file of new version. Otherwise your translation pack will not be working properly on new versions.