To edit your subtitles, all you need to do is click on 'Style' right under the video.
The screen to the left will project how your captions will look.
Changing the subtitles' size
On the Subtitle editor, you can change the size of your captions. Under 'Font' select the font size you need.
I don't see the Style option
If you uploaded an audio file for subtitles, then the Style option is not available.
If you uploaded a video file and the Style option isn't appearing, let us know and we'll try and resolve this for you.