How do I combine slides from two different PowerPoint presentations?

There are two methods to combine slides from two different PowerPoint presentations.

Method #1

1. Open both PowerPoint files side by side so they share the same screen.
2. 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. It does not affect the slide in the original presentation.

Method #2

1. Open the PowerPoint you want to add slides to.
2. Click in the space in the slide side menu to mark the location where you want slides from the second PowerPoint to go.
3. In the Home tab from the top ribbon, click Reuse Slides. 

4. In the menu that appears, click in the text box that says Search OneDrive, SharePoint and this PC. 

• Enter the file name of the presentation you want to copy slides from or scroll down to browse the suggested list and choose the file from there.
• Click on the file to view the slides.

5. Find and click the slide you want to insert. The new slide should appear in the presentation.

NOTE: Checking the box Use source formatting at the top of the Reuse Slides​​​​​​​ menu, below the File name 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.