getting my students onto Khan Academy after creating their accounts

Hello,  I am trying to understand the process of getting students under 13 logged in to Khan Academy.  I have created their user names and passwords and have a class code.  I would like to assign work for them. But, I have 25 students and I need to be able to have step-by-step instructions for them to login to their accounts.  Do they or do they not need an e-mail address?  Can students login if they have a class code, user name and password? If they still need an e-mail address it seems like an extra step on top of everything I've already created.  Please help! I've tried going to the Khan Academy site and attempting to login as a student and unfortunately it is very convoluted, so I don't think my students will understand what to do unless I know and am able to anticipate the challenges.