You need to add a Static Mesh component from drop down list, and then see top image above, in details panel set the “Static Mesh” to SM_SkySphere (or whatever your sky sphere is named).
Hope that helps! 
You need to add a Static Mesh component from drop down list, and then see top image above, in details panel set the “Static Mesh” to SM_SkySphere (or whatever your sky sphere is named).
Hope that helps!