For MuseScore 3 users, see Helping to improve translations
Do you have a translation to add? That can be done easily via the web, as mentioned in Development / Translating ...
- Ask in the forum to improve translation
- Connect to Transifex/MuseScore http://translate.musescore.org, which will redirect you to https://www.transifex.com/projects/p/musescore
- Select the language and then the section you want to help with (musescore or instruments)
- Click on the "translate" button (the button text will depend on your language...)
- Search for "strings" (informational meaning) you want to translate (you could filter "already translated items")
Here is a technical explanation: Continuous translation for MuseScore 2.0