Play games
Choose the game that interests you and play itfor free.
Complete the tasks
Every game has some tasks 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.
One time, I opened the Glove Case and actually got a paid of gloves that were worth $300. I couldn't wait so I bought a bunch of games I wanted.