Dare to travel the absurd and dangerous Orion Trail, where only the luckiest, bravest, and most stubborn captains will make it all the way to the end. Become famously incredible or incredibly dead in this single player choose-your-own-space-adventure!
Go to: http://store.steampowered.com/ and download STEAM client
Click "Install Steam" (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don't have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam...
Follow the onscreen instructions to complete the process.
After successful code verification go to the "MY GAMES" tab and start downloading.