Sins won't be made available digitally until it ships to retail outlets in North America. We have setup additional bandwidth and server capacity for the release, however.

In terms of digital downloads - the easiest way to handle this is with a Stardock.net account (it's the same as your forum account here). Once you tie your serial to it in Stardock Central (by registering), that's all you'll need in the future. If you do need your serial again, you can put your email address into a support form and it'll be sent to you.

Pre-orders haven't been charged yet. Odds are you only have an order number. You won't be able to obtain the game until it's released.