Family Sharing verification code access issue

trying to set up family sharing. i followed the stages from my iPhone. add members, fill in all the necessary detail, set up a i cloud id for the child, then it asks for the verification code which is sent to the child's ID that i just set but there is no way of access this code. ive tried logging into icloud and apple with the new child's details and my own. what am i doing wrong? please help.

[Re-Titled by Moderator]