1/4 Add a text caption box and make the background transparent
Insert > Standard Objects > Text Caption.
Click once on the caption box.
Properties > General > Caption > Select 'transparent' from the drop-down box.
2/4 Type the following in the caption box:
Slide $$cpInfoCurrentSlide$$ of $$rdinfoSlideCount$$
3/4 Settings for the new caption box
Place the new text caption in a suitable place on your slide.
Properties > Timing > Display For: rest of project.
You do not need to paste the caption box anywhere else as it will now appear automatically on every slide.
4/4 Test it out
Publish the project, check the positioning of the text and adjust if necessary.
Find a full list of Captivate system variables here.
Read more about how Captivate's system variables work.