also, if you have the atmosphere panel open and have realistic sky selected, you can drag and drop an atmosphere into it from the browser section of the panel below the workspace window.  Mind you, not the tab that says Scenes but rather the tab that says Misc.  Select it and then you see a list of categories.  Select realistic sky.  Any of those skies can be dragged into (onto) the atmosphere panel.  No cameras or lights will be set - you will have to recheck Enable Ground to off if you want it off or if it was already off from a previous go round.

Also, it might not look like it has worked (unless you did have the enable ground off because it will be checked after the drop).  It doesn't otherwise give any indication like some drag and drop functions that show a plus sign once you arrived where you want to drop