To file a separate return for a dependent in the Online version you need to set up a new account separate from yours. Online is only good for one return per account. You can use the same email address for 5 accounts. You can probably use the Free Edition
Https://ttlc.intuit.com/questions/1894512-how-do-i-start-another-return-in-turbotax-online
Be sure on the dependent return you check the box that says you can be claimed on someone else’s return. If their only income is W2 and under 12,550 they do not have to file a return except to get back any withholding taken out.
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...
