How add subtitle file .srt

Here is the help file:

https://helpx.adobe.com/premiere-pro/using/working-with-captions.html

Import the .srt to PR. The default for .srt is Open Caption. Once in PR, you cannot convert the Open Caption to Closed Caption.

Before you add the .srt to a timeline, make sure it is the correct pixel size. PR sets this on import. Change by: right click on .srt in project bin and Modify -> Captions.

All you can do with Open Caption is burn into movie on export, or export the .srt.

There have been many problems with captions and subtitles. And recent versions have made a number of changes. If this doesn't work, report your specific dot version of PR. (Help - About Premiere Pro.)