You didn’t upload it anywhere. The exporter options just help you get it ready for sharing when you do upload it someplace, like flightsim.to.
A “World Hub” is coming to Flight Simulator at some point, and in that case, you would be sending your changes to every other user when you submit. It’ll be pretty clear that that’s what you’re doing though. And I hope it arrives sooner than later as user edits to the scenery will vastly improve the game.