How to Add Subtitles to an MKV File
Matroska (MKV) is a multimedia container format used to play high-resolution video. MKV can be customized for multiple subtitle and audio streams. Subtitled MKVs are popular with users who watch foreign-language media. MKVtoolnix is a freeware program which allows a user to add his own subtitle stream into an MKV file.
Things You'll Need
Download and install MKVtoolnix from videohelp.com (see References).
Click "Add." Select the Matroska (MKV) file from the Explorer window. Click "Open."
Click "Add." Select the subtitle file from the Explorer window. Click "Open."
Click "Start Muxing." Wait for the muxing process to complete. After the completion, the Matroska (MKV) will contain subtitles.