1. Open PowerPoint and create a new slide.

2. On the Insert tab, select Picture, and then select the picture you want to insert from your computer. You can insert one or more pictures.

3. After inserting the picture, you can select the Format tab to adjust the size, position and style of the picture.

4. Next, we need to set the rotation effect of the picture. Click the Transition tab, and then in the Switch to this Slide group, select the transition effect you like. Such as "fade out" or "advance".

5. In the Timing Group of the Switching tab, you can set the switching interval. For example, you can set it to switch every 5 seconds.

6. If you want to set the playing time of each picture, you can set a separate animation effect and time for each picture in the Animation tab.

7. Finally, you can preview your merry-go-round effect. Click the Slide Show tab, and then select Start from scratch.

The above are the steps to make the PPT picture carousel effect. It should be noted that there may be some differences between different PowerPoint versions, but the basic steps are the same. In addition, you can also download plug-ins or use professional PPT production software to produce more complex carousel effects.