How to load a subtitle using BS Player

[BSPeter]

Unfortunately you fail to mention the type of your subtitles.
In this connection please read item (9) of my Help2Help-post (a.k.a. "READ THIS FIRST BEFORE POSTING") with respect to which subtitle-files BSPlayer supports natively.
If it is e.g. a Subrip (.srt) subtitle-file, it can be loaded manually after having loaded the video-file, by a right-click followed by selection of "Load subtitles" ...etc. (Most skins also have a button for this.)
However, if a subtitle-file is placed in the same folder as the movie-file and has the same name as the movie (except for the file-extension of course), you need not do so, as it will then load automatically (unless you've disabled subtitles under (rightclick >) Options > Preferences > Subtitles.
If subtitles are correctly loaded (either automatically or manually) some skins (control panel) will show the name of the subtitle-file.
If filename is shown there, BSPlayer has recognized it (and able to play).
If in spite of that still no subtitles appear please check setting under
(rightclick >) Options > Preferences > Video > [Video rendering]
Try a different mode; e.g. no overlay or "Use overlay Mode 1".
Any difference? Other settings to check are those under Options > Preferences > Subtitles (e.g. "Draw subtitles to Overlay surface").
Also it could be of interest to check (with movie loaded) under
(rightclick >) Options > Filters > Advanced
what codec/filter is actually used to show your movie (as there might be a conflict as some are also able to display subtitles as mentioned in item (9) of my Help2Help-post.