YouTube website provides a function for users to upload subtitles. The recorded audio is separated in seconds and each column with clear time split is provided for you to key in the lines.
If you are writing on a transcription file and plan to copy and paste line by line to YouTube, be ready to go through a lot of tedious work. It could be painful.
If you are writing directly on the pre-set YouTube lines, you can see your subtitles on the video immediately. But the thing is, you have to copy your lines to another Word file if you want to save a copy.
You might need to go through trial and error before you get used to it and find your own way to get your subtitles uploaded.