To properly view the assembled sprites and all their animations (as some may not included in the "Assembled Sprites" folder due to size), you need to drag the files in this folder (the .atlas, .skel, and the sprite sheet) into a program that can view Spine animations. The one I would recommend for its ease of use is SpineViewer program by ww-rm: https://github.com/ww-rm/SpineViewer.