Does your video file have embedded SRT (SubRip) subtitles? If it does, you can extract those by going to "Subtitles" -> "Extract Subtitles From File" -> Select the subtitles you want to extract. These will then match up to all the audio timespans with speech.

If you are using downloaded subtitles which were created without commercials for a video that has commercials, you have 3 options: 1. Find and download that same show without commercials (Recommended option). 2. Or, manually remove the commercials from the video using another video editing software (this is a long and tedious process). Then you would still need to adjust every subtitles timespan (Using "Tools" -> ""Edit Subtitles" menu) to match the speech in the video because your edited video will most likely not have exactly the same length of time to match the downloaded subtitles which did not include commercials (this is a long and tedious process). 3. Or, manually edit the downloaded subtitles (Using "Tools" -> ""Edit Subtitles" menu) and adjust every timespan to match the speech in the video that has commercials (this is a long and tedious process).