Subtitles are created for specific "releases" (HDTV, BluRay, Web-DL). If the text is off-sync, your player (like VLC) usually has hotkeys (G and H) to shift the timing forward or backward.

Subtitles are typically included as a standard toggleable option under the "Audio & Subtitles" menu. 📂 Third-Party Subtitle Databases

Most players will automatically detect and play the subtitles.