Since .mkv files are containers, they usually have "soft" subtitles. Use the Subtitles > Sub Track menu in your player to turn them on.
If you are looking for a "guide" to this specific episode or how to handle the file, here is the essential info: 🔍 Identifying the Content
Scan the file with VirusTotal if you are unsure of the source. What show is this supposed to be?
Are you having a (no sound, won't open, etc.) with the file?
Since episode 103 is a specific milestone, it likely belongs to one of these long-running series:
run an .exe or .bat file if it was included in the download.
Use VLC Media Player or MPC-HC to ensure all video and audio codecs are supported.