You can use Impulse (Stardock's digital distribution software) to download your game.  Impulse will give you the ability to resume downloads, as well as notify you when updates are available, and prompt to update.  It will also automatically activate any of our products you install.

You may download Impulse here: http://www.impulsedriven.com/impulse_setup_full.exe .  Once you've logged in with your Impulse account (the one you use for these forums), and Impulse finishes any additional updates needed, you can now go under the 'My Games' tab in Impulse and select your product and click 'Install' to install it. 

If you bought your software directly through the Stardock or Impulse store, the registrations will be added automatically into Impulse.  If you have a retail bought title and need to register, click on the help icon in the upper right of the Impulse interface (the one that looks like a blue circle with a question mark) and select "Register a product with Impulse".  Once on the registrations page, in the bottom right, click the 'Add Registration' button.  In the Window that appears, enter your serial number (Remember all serials use letters A-F and numbers 0-9.  Dashes in the serial number are important and must be included), followed by your e-mail you used to create your Stardock.net account, the product category and the product name (If you serial is recognized, these last 2 will be auto filled).  Click 'Add Registration' button and you've registered your product.  This will register the software to your account, and get you the latest updates to your product, as well as keep track of the serial number if you ever need to install again.