Using a separate narration file: timing

[sagestrat]

This is the first time I'm adding a separate narration file to an existing Powerpoint file. I know how to add the file as an audio file, but I don't know how to match the timing of the slides to the narration. End game: I want to post the file (with the narration) on our website for others to view. Does this require me to make a Powerpoint movie? Don't mean to have such a basic question, but I haven't done this below. Thanks for any guidance.