From the inventory you can pick and choose the skybox from the list of options you have or if you are looking for a specific type of skybox use the drop down menu to break it down to the particular type you have available. The more types of skyboxes you have the more options will show in the drop down list.
Now that you have found the perfect skybox for your idea let's apply it
Go to your decorating tools (the one that looks like a chair) and choose Skyboxes
Basic Decorating 101 = the Basics - Environments
Nuvera Online