Hi Enyon,
Once you've translated all the existing original subtitles, you can use the "Convert to timed text" option in the translation interface, and directly make translated subs from the video for the rest.
See Anatomy and Use of the Translation Interface in the documentation, which has a screenshot, and an explanation under point 4.
Enyon Eugenisu
Ok so if there is already an incomplete transcription in English on Video, and I have started new subs in another language Amara don't seem to let me add more subtitles and I am limited only to translate English text. How do I add more subtitles then there are in original English. Don't see any way to switch to the interface with tab buttons and play back... So I can't add more subtitles.