Adding Image Sets
Organize versions of your images in image sets, which you can add to an asset catalog.
In the project navigator, select an asset catalog.
In the Finder, select an image and drag it to the set list in the selected asset catalog. A new image set is automatically created.
Alternatively, you can create an empty image set by choosing Editor > New Image Set.
To add another image to the image set, drag the image from the Finder to the appropriate image well in the set viewer.
Alternatively, you can add images by choosing Editor > Import.