Once you ordered the app, you should have received an unique product key (visible on the receipt page once you have paid it). You can use this key to register your application in Impulse (Registrations -> Add Registration). Once you have added it there, it should show up in "My Games".
I noticed that if you pay using PayPal the receipt you receive on your email won't contain the product key. In this case the key is available only on web. In case you lost the key, try contacting Stardock with your order details. Hopefully they will be able to help you.
All the best. 