Top notch rhyme... just like a lime?...
Yes, in a more clear form:
Once you have your serial open Impulse
Presuming you have an Impulse account (if you bought through one use that one) click settings (the blue button to the left of Explore)
Click 'Register a Product'
At the bottom right click 'Add Registration'
Fill in the Blanks!
Your game should show up under the 'My Games' tab for you to download and install. And Yes, the download feature allows you to play the game before the CD arrives.