If you've never translated for TED, start here. If you're having issues with your application, we can help here too.
Once you've applied, follow this guide to find talks in your target language(s).
Translating TEDx Talks
First, read the above guide to translating TED talks first, then check out this OTPedia article for tips on working on TEDx talks.
This is a link to the general Amara documentation, in case you need any more information on the platform.