You don't include their income on your return. It would only go on their return if they are required to file one. To file a separate return for your dependent you need to set up a new account. Online is only good for one return per account. You can use the same email address for 5 accounts.
How to start a new online free return here
TurboTax® Free Edition: Free Online Tax Filing
Be sure on their return they check the box that says they can be claimed on someone else’s return. If their only income is W2 and under 14,600 they do not have to file a return except to get back any withholding taken out.
Filing requirements for a dependent
If you are using the desktop software, you can start a new return and enter your child's information and earned income. If you are claiming the child as a dependent on your return, be sure to mark the Someone else can claim me box on the personal information screen on your child's return.
If you are using TurboTax Online, you will need to create a new account for your child. The Someone else can claim me box will be in personal information section, labeled My Info. Only mark the box if you can still claim your child on your tax return. Who can I claim?