To use your image for an application or document icon, just save the image as an ICNS file and add it to your application's project.
To use an image as an icon for a file or folder, add a factory with the format Icon for File and set the path you want to change the icon for.
To export a set of icons, put them together in an image file with frames and export them either as an iContainer file (which will hold all of the icons) or by selecting one of the special Frame factory options (Folder of All Frames, Zip All Frames, or Preview of All Frames) to save all of the image's icon frames.