- Open the main PowerPoint.
- Click in the space in the side menu to mark the location where you want the slide/slides from the second PowerPoint to go.
- Then select the Home tab on the ribbon. Click on New Slide, then select Reuse Slides.
- A menu will appear on the upper right side of the page.
- Choose Browse, then Browse File in the right side menu to navigate to second PowerPoint file.
- Select the PowerPoint file that contains the slides you wish to use and click Open.
- You should now see the 2nd PowerPoint in the side menu. Right click on the first slide to Insert Slide or Insert All Slides into the main slide show.
Another quick method is to open up both PowerPoint files, side by side (so they share the screen). Drag and drop slides from one file to another. The slides that are dragged over duplicate in the file you are copying them over to. This does not affect the slide in the original presentation.
NOTE: Checking the box Keep source formatting will keep the second design theme when it is added to the main slide show. Leaving it unchecked will convert the second design theme to the main slide show design theme.