Open a page in your book and select the image on the canvas.

In the toolbar above the image, click Crop image.

Drag the blue corner handles to crop as needed.

Click anywhere outside the image to finish.

Select the image you want to replace.

In the toolbar, click Replace image.

Use Image Tags or the Search images bar to locate a new image.

Hover over the desired image and click Select.

The new image will appear in place of the original.