So you dont actually get 5 coins for registration as there is no place to enter the code for 5 coins they mention in OP
Hi Kid_diK,
Sorry you're having trouble redeeming your code. You might be looking at the Vietnamese version of the site, which currently doesn't have the invitation code box. We're investigating this, but in the meantime, please change the language to English at the top right and you'll find the invitation code box beneath the email address and password boxes when opening your account.
If you still have trouble, let me know.