Agree to the Translation Center Terms of Service and choose the language you want to translate to. Note: You will only have to do this once and cannot change your language, so choose your native language or the one you know best!
Check the language guidelines in the language forums. Click on the Forums tab at the top of the Translation Center home page and find your language forum, under Language Discussion. (You’ll see a post stickied at the top with your guidelines in it.)
When translating, you should use the glossary set out for your language by the moderators and community. You can access this by clicking the Help tab at the top of the page and then selecting Glossary in the drop-down menu.
On your Translation Center home page you'll see categories - twitter.com, mobile.twitter.com, Twitter Help, Twitter for iPhone and iPad, Twitter for Android, and more. Select a category.
Once you've chosen a category, you’ll see the project tags which contain phrases to be translated.
Type your translation in the box next to the string and remember to hit Save Translation when you’re done.
On the side of your home page, you’ll see the top translators for your language along with their levels. The more quality translations, votes and approved strings you submit, the higher your translation level will rise. You can also click "More information" to visit the permalink page of the string to see more translation options. This will allow you to vote for other translations, see context notes, similar phrases, comments from other translators, and other relevant information.
If you want to add your own comment, you must first allow the Disqus app to access your account (you only need to do this once!), you’ll then be able to submit your comments any time.
If you like an existing translation and don’t want to submit your own, you can always vote for the best of the existing ones.