The beta for Sins of a Solar Empire: Rebellion is going out, and in case you weren’t aware you will need to install and use Steam to get access to the beta. If you are new to Steam or not familiar with adding games, then this is a quick how-to so you can get it done quickly and get gaming sooner!
Download Steam - http://store.steampowered.com/
You can find your Rebellion key in your Stardock account or in your beta e-mail.
Once you have your key and Steam installed, open Steam. At the bottom left click ‘Add a game’ and select ‘Activate a Product on Steam’.
Next you have a new window with a couple of screens with agreements, instructions, etc. You will then be prompted to enter your key.
After that, you will get confirmation and install info screens.
That’s just about it. You can click the downloading area at the bottom of Steam to open up your downloads, and you can also view them from your Steam library.