Need Help To Get Stardock 10 Working

I need help. I just purchased a new computer with windows 10 which I cannot stand so I purchased the Stardock 10 Software. I downloaded it successfully with the product key, but my windows 10 theme still remains on the desktop. I do show the Stardock start button, but I do want my screen to look like Windows 7. I have tried several times. What do I need to do? Thanks for your help!  Sue