First, create an account in GitHub if you don’t already have one.
Then go to the offical code for Memmy here and create your own fork of it.
Then, after you’ve done, you can create a pull request (i.e. a request to have your code added to the official repo), see here for an example.
I'll make a post about this later, but for now stickying this thread and you guys should follow ^^^ if interested in doing this. Huge help if you can!
@lacarsi@lemmy.ml, I'll see if I can do the PT translation tomorrow, should have some free time, and @gkd@lemmy.ml, if I can make a request, would it be possible to add an option to toggle the app language, either in the settings app or in memmy itself?