Netflex

When we had T-Mobile family sharing for Netflex, our son put netflex under is e-mail and password.  But now I understand that we can only have Netflex in our home since this is our account.  Can I change the log in to me. 

Also, I read the other day that I could add him as a user for $7.99, but now I can't find it.  ¿Me pueden ayudar?