Just go to your account page under My Products and it will be on the list. Unless you never registered it. 
If it is the X1 LE version I would not bother, I have it myself and it is the very worst version of Sonar so not a very good example of where Sonar is at now. If your short on cash a much better solution is $50 for Sonar Home Studio which is bug free and is up to date with W7 and 10. It also allows you to run in WASAPI mode if the Boss didn't include ASIO drivers.  
It comes with enough VST to get going, much better stuff than LE has. And for free and cheap you can add 3rd party stuff. 
Example the Air Complete bundle is on sale at JRR shop for only $56 US and that is all you'll every need. Home Studio with the Air bundle gives you almost more than you get with the $500 version of Sonar and that's only $120 spent.