Get the Rev .srt file with the subtitles for the video. Download the file.

Login to Wistia.

Click on the Project that will contain the correct video to be subtitled.

Click on the Video to open it.

Click on Customize > Captions.

Toggle Captions ON and click Captions on by default

Click Upload .srt file.

Then select the correct file from your Downloaded files list and click Open.

Play the video and watch for subtitles to appear.