I made this
translation guide that has all the info you need. Here is the
English addon you can use as a base or to just compare with the Portuguese tags to make sure everything matches.
You two will need Oak to translate some of the tags. Private message
Melekor over at Magma forums asking for access to Oak. After you are granted access, you will notice the Private Testers section. Look for the most recent Oak build thread and a download link will be at the first post.
I still need to build the Portuguese addon before you can work on the translation, but for now you can check out the guide and message Melekor.