https://www.indiegala.com/store#giveaway

Scroll down to the bottom and there’s a giveaway banner.
You must join steam group and set profile to public to receive the key. You can always set it private or whatever afterward.

If you have a problem, try these steps.
1. Join Indiegala steam group and set steam profile to public.
2. Log out of Indiegala site and re-login and then proceed to the steps with giveaway.