As BSPlayer uses text-based subtitles, you could - in principle - even do it "entirely by hand" using Notepad. Just open an existing subtitle file (in .srt, .txt or
(text-based) .sub format in Notepad to see its structure; if its is no text-based subtitle-file you will get a lot of rubbish on your screen instead of readable subtitles)
Creating a subtitle-file in a text-editor like e.g. Notepad would however present a rather elaborous job, so I suggest you use a utility like e.g. Subtitleworkshop.
Have a look at
this post here for some links.
