Camtasia produces videos. There are no "slides". But you are able to insert callouts that pause playback. You could use those.
Note, however, that you cannot force this behavior if you publish to YouTube or Vimeo. You must play the video using the associated files created by Camtasia when you produce your output. Or, you could upload your video to ScreenCast.com. That would work too.
hope I'm right about this; been many years since I've worked with PPT ...
in case the poster was referring to viewing a PPT slide show, and manually advancing to the next slide[s], then simply set up the PPT slide show, start a capture of the slide show area on your monitor, then run through the slides; end capture when finished with all the slides; this would be a normal screen capture and not a capture using the PPT plugin