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.
Don't waste your time with this quest. It rejected me for not being registered, but you can't register with this game. Only google play sign-in and Facebook.