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.
If you struggle to find where the needed information is to confirm you played the game twice in 24 hours as the task tells you to do, like I did, you can find it in the 4game launcher. Open your profile, and then click on "Activity log".
I can confirm this works, my task got accepted.