How can I create Circle JigSaw Puzzles?
Puzzle Maker Pro - JigSaw Circles supports most of the features of JigSaw Squares (for which there are a lot of tutorials). However, some things are very specific for Circles.
Circles
First of all, the JigSaw Circles will only create a circle (or oval), it will not fill out the empty space along the border of the image. That means a significant part of your image will be cut off - it makes sense to prepare images that have the actual image centered.

Number of concentric circles
In general, the number of concentric "Circles" should be 2 or 3. Due to the nature of these puzzles, pieces will be quite small when you have 4, 5 or more concentric circles.
Circles and Ovals
The option "Perfect Circle" will enforce the resulting puzzle to be an actual circle. Without this option, it may be an oval. This can be used in some cases, but since it easily gets ugly (esthetically), Puzzle Maker Pro - JigSaw Circles has not been optimized for extreme settings. The screenshot below illustrates the effects of using an oval where the height and width differ a lot:
In addition to this esthetic effect, the puzzle page (showing the separate puzzle pieces) may show overlapping pieces, because the sizes of the pieces differ too much.