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've recently noticed that I couldn't get my weekly chests even though I logged in 7 days a week. Thought it was a part of the summer adventure event. I still can't open it after the event