Basically upload the subs to youtube, then redownload as .VTT file.
Open it in notepad and add: line: 10% to the timing, so it looks like:
00:00:06.120 –> 00:00:11.120 line:10%
how to change the text colour
and positioning of captions.
See:
https://medium.com/@mlockrey/how-to-change-the-positioning-of-captions-in-youtube-c75bb9ac0aff