I am venturing to guess that you want to use the WIDGET and not the PROGRAM:
The ATK WIDGET will kill all apps that have not been placed into the "ignore list" within the menu of ATK PROGRAM. When you "press" the WIDGET ICON you will see nothing other than a dialog that tells you how many apps were killed and how much free memory you have. In contrast, the PROGRAM will display a list of running apps and allow you to select/unselect which ones to kill and manage the applications settings.