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.
Gamehag should add tasks with rewards for soul gems for more browser games that can be played on PC. I don't really game much on my phone and would prefer if there were more games in the PC browser game section with similar rewards to the mobile browser games.