Hi André,
It’s great that you are interested in helping. As discussed previously, the first thing that you should probably start by doing should be establishing a glossary for the most basic terms. E.g. “how should we translate ‘conference’?” or “what is the best term for ‘call for abstracts’?” Transifex has a glossary feature which you can use to document that.
We’ve got a wiki page on i18n which should help you understand how this works from the point of view of a developer and what are some of the technical details involved.
There is at least another person wanting to help with the translation to Portuguese from Brazil. I hope they will join the discussion here, so that we can distribute work in an optimal way.