You don't enter a dependent's W2 or income on your return.  It would only go on their return if they are required to file.

https://ttlc.intuit.com/questions/1901296-how-do-i-add-a-dependent-s-w-2-to-my-return

How much is it?  If that is the only income he has he doesn't have to file if it's less than 6,300 except to get back any withholding taken out.  If it's over 6,300 he has to file his own return for it.  Be sure on his return he checks the box that says he can be claimed on someone else's return.  

Online is only good for 1 return.  But you can use the same email address for 5 accounts.   How to start another return in the Online version      https://ttlc.intuit.com/replies/3288574