Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
I'm not exactly sure how you do this because signing up through the war thunder page just brings you to the download button. Anyone know how to "Create a new account through gamehag"?