Carousel Adding Images
In order to add images you will need to select a group then adjust the "Slide Image Dimensions" width and height so that the Carousel plugin will know what dimensions it will need to resize the images to.
After saving the desired image dimensions then you can add an image by clicking the "+Add image" button. Carousel uses WordPress's built in media up-loader. This will allow you to either upload new images or select images that you have already added to the media library.
In order to select an image to add from the list of images click the the image you'd like to use and then click the "Add Image" button as shown in the image below.