To load each of the images, select the image name (main, task, tracking, selected, disabled, slider-normal and slider-mouse down) in the Image Selector (number 3 on the main image above). This will display the current image for that state. Click on the folder open under tools in the toolbar, or use the menu Edit | Load Image and select the image. Your image should now be displayed on the interface. Repeat for all the image states. If you do not have all your images yet, you can simply load the main image into the unused slots and leave the sliders as default.