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 have ordered a reward for 3 days and the site haven't delivered it. I read in FAQ and they said the product will be delivered in 72 hours.