Subtitles-made file but doesn't work after import into MC

Hi there, 

I made a txt file according to online tutorials with <begin subtitiles> and <end subtitles> and the timecode of where each text should go, but when I imported this into Media Composer using the SubCap tool onto a separate track in the timeline, the subtitles do not appear (ie. are not chopped up and placed in the right timecode places). How should I solve this?

Thanks,

Yun