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, when I signed first signed up for Neverwinter through gamehag's link, I never received a 'confirmation' email. My initial screenshot was rejected with the reason of my not having a 'new' account with arc or neverwinter or whatever.
Just recently, though, I discovered that in the arc desktop client, if you open notifications, you will find one that asks you if you want to send a confirmation email. So, to those who are wonder why they haven't received such an email, it's probably because it's not automatic.
I uploaded a new screenshot for gamehag and hopefully I won't get rejected this time :D
EDIT: That seems to have done it. My task was accepted. If anyone is facing a similar rejection and hasn't seen any sign of a confirmation email, check the arc software client.