Taken from the FAQ
Or simply go to https://inovaestudios.com/Battlescape/Access
And link your steam account.
Q. If I pledged to your crowd-funding campaign, will I have access to the game on Steam ?
A. Yes, although we cannot confirm that everybody will have access to the game on Steam on the day of the launch. In the worst case, we’ll provide backers access to Steam [ providing Steam’s acceptance ] in the days following the launch.
The way it will work, you’ll simply go into your I-Novae account profile and authenticate on Steam. Doing so will provide us with your Steam user ID, which we’ll then automatically use to associate the game to your Steam’s library. There are no keys involved in that process.
Extra game copies ( higher tiers ) will use a separate process, which we haven’t figured out yet, and is unlikely to be ready for the launch.
Q. Do I need an I-Novae account to get the game on Steam ? How do I create one ?
A. You must create an I-Novae account with the same e-mail than you used on Kickstarter or IndieGoGo. You can verify that your pledges are correctly detected on this page:
https://inovaestudios.com/Battlescape/Access
The game is currently in closed beta, but will step into Early access on the 27th of September. At that point, backers will receive permanent access to the game through our own launcher, and shortly after ( ideally on the same day ) will be able to associate their account to their Steam’s library, and play the game on Steam.
Q. I already have an I-Novae account but it uses a different e-mail address than the one I used for pledging, what do I do ?
A. You can add a secondary e-mail address to your I-Novae account settings:
https://inovaestudios.com/Account#/
Q. I changed my e-mail on Kickstarter / IndieGoGo since I pledged in 2015. How do I use my new e-mail address ?
A. There is currently no automatic way to do this, as we are matching your I-Novae account to the e-mail that was used for pledging no matter what.
To verify your identity, please send us a private message from your Kickstarter or IndieGoGo account, and include your new e-mail address as well as your pledge ID#, and we’ll manually update our records as soon as we can