Select images for the Pie Medical interface

Open the interface and click on 'Toolbar On' in the menu. You'll see that the Pie selection tool has been assigned to the left mouse button.
Display the image you want to analyze using the scrollwheel or the scrollbar. Press the image with the left mouse button or, if you've assigned the Pie selection tool to the right mouse button, with the right one. You'll see that the selected image appears in the Pie interface.
The red numbers displayed in the interface images are the image number and the sequence number in the overview window.

Remove any image from the interface by right-clicking it and choose 'Delete'. Press 'Clear all' to delete all images and disable the 'Pie image selection' tool by assigning a different tool the mouse buttons.