I don't understand your question.
Every separate game you've got saved is a "park" shown on the list of "my parks". You can upload them all. However, you always upload a copy of the park in the same state that it was last saved in. IOW, you start a new challenge or sandbox park so it's just flat, blank terrain. You can save it in that state and upload it like that. Or you can build a complete park with dozens of rides, shops, and thousands of customers, save that, up and upload it. And everything in between.