Hi

. . . . I cannot find the way to crop this off whilst in Photostory . . .

The cropping tool is called Section, and is found on the fX tab under View & animation, Section

To crop, set the require options circled in the image below, then drag any of the handles arrowed to set the section required - side handles are also shown in the image but not arrowed for clarity.

When you deselect the image in the timeline the effect will be applied, as shown in the second image where a light crop has been applied.

Result

HTH

John EB