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.
So it looks like their link to the web-based version is moving to the dl client. I just notified Gamehag that their play link is broken. I cant find the Web Version as of today. Just FYI to anyone starting or trying to complete the GH quests.