Hi Michael,

Not sure which version of PPT you have, but the later years are close to being the same. Go to "View" menu in both presentations. In view select "Slide sorter" in both. Click on the slide you want from the presentation in the slide sorter mode until it is highlighted, right click "Copy" or Control/C on the key pad, go to the presentation you want to paste it in, place your cursor and click before or after any slide where you want to paste it, and right click "paste" or Control/V on the key pad. You can then click and drag the slide to where ever you want it in the presentation.
Hope this helps.