You can change the title and title translations of your videos easily. Start in the left sidebar and click the Content tab, then 'My Content'.
Scroll to find the video you want to edit the title for. It will show up like this in your list:
Click the thumbnail of the video, and a box will pop up. You can change all of the information for your video here: thumbnails, titles, tags, pricing, metadata. In the first tab ('metadata') you can change your title and its translations.
When you're done, don't forget to save your changes.