Can I add the software to my existing website?
No, you cannot add the software to your existing site but you can leave your current site active pointing to the software. Below is an example of how this can be accomplished:
Leave your current site live, pointing towards www.yourwebsiteaddress.com
Somewhere on your site add a link or some type of redirect to store.yourwebsiteaddress.com
There are many ways to accomplish this and this is only one example.