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.
when submit a screenshot, just don't crop it, submit the whole screen (with the window start button). In Crossout, play in window mode and take a screenshot. I did it and got accept for all 3 games when submitting only 1 time.