To participate in the translation effort, go to [the MultiMC crowdin site](https://translate.multimc.org) and join the project and get in touch on [discord](https://discord.gg/rjpzCxvAPQ).
(If you don't have a Crowdin account, you can create one using your Facebook, Google, Twitter, Github, GitLab or any other email.)
You may want to use [POEdit](https://poedit.net/) to work on the translations. MultiMC allows putting a `.po` file in the translations folder and see changes in the application as you translate. Combined with its Crowdin integration, this is pretty powerful and comfortable to use.