Existing accounts

I used this program last year for our Math Olympic competition preparation.  Im in charge again, so I convinced admin to pay for it this time and for  other teachers to be able to use it.  Some of my students that used it last year are showing as existing accounts.  I have new login and password information, so must be pulling from database.  Is there a way to correct this?  It is bringing up their last year grade levels and not allowing them to access account.  What is the best way to enter in new students? What does comma separated emails mean?

M Lewis

8th Grade

Lakeside Elementary

559-974-6930