Online is only good for 1 person and 1 return. To do another return you need to set up a new account. You can use the same email for 5 accounts. If you have the Desktop program it can do multiple returns and efile 5 for free. Sign in or start a new online account here,
https://turbotax.intuit.com/personal-taxes/online
If their only income is W2 and under 14,600 (2024) they do not have to file a return except to get back any withholding taken out. If they got a 1099NEC or cash that is self employment and they have to file for any amount.
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-d...
Be sure on their return they check the box that says they can be claimed on someone else’s return.
