You will need to create the accounts in Code.org and make sure you sign in (I used my school issued Google account).
Once logged in - select the My Dashboard (upper left of screen).
From there you will need to add your students and decide how you would like their passwords created.
Once you select save - you will be able to print their cards.
Embedded below is a GIF followed by a 1 minute and 51 second YouTube tutorial.
Take care and enjoy coding!