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.
So I've completed the Game of Thrones Task I and got an e-mail saying; "Game of Thrones Winter is Coming - task accepted! Screenshot confirming completion of the task has been verified and accepted." Then when I checked out my account I got another message reading: "Task has been verified once again and has been rejected" I send another Screenshot and once again it gets accepted only to then being rejected a few minutes later. And I'm still waiting for the War Thunder task feedback, which I finished first thing today.