Click on your avatar in the top blue bar, then on "Downloads". You should arrive here: https://store.stardock.com/myaccount/products
Then, in the Software tab, click on "View Individual downloads" In the Object Desktop tab. Then just scroll down the list until you get to Skinstudio 10 and 11. All the software you're entitled to should appear on that list, btw.
Then dl and install and you're on your way.
edit: Oops, I see basj arrived first. I'll leave this as it might answer further questions.