With respect to the Speech to Text, assuming you downloaded a text file, I do not have Speech to text available to me, then I think you need to you copy and paste its contents into a Title, as for any of the online speech to text generators, and format it from there.
SRT files are for direct import when uploading video, the srt is uploaded separately, to YouTube and Vimeo. Video deluxe cannot import srt files and create the titles.
If the final video is going to be uploaded to YouTube see this article.
If not uploading to Youtube or Vimeo, to add the subtitles directly in VDL, this has to be done immediately after the audio analysis, click the Create titles shown below
Note: the AI speech to titles may throw some errors trying to translate a strong Scottish accent, it produced some real bloopers with a mix of English and German giving both translation errors and/or German word spelling errors.