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 think i's a big waist of time every match takes over 30 mins I think specially when you're so addected to it it becames like a black hole that you can't escape from it :(