My children paid taxes and W-2 for summer job, how do we get those taxes back?

[AmyW]

You should not claim your child's W-2 or self-employment income on your return even if you claim him as a dependent. The dependent would file his/her own tax return and should check the box Someone else can claim me on their tax return in the personal information section. 

For more information see below:

https://ttlc.intuit.com/replies/3302077

If you want to file a tax return for someone else, then you will want to create a new TurboTax account because only one tax return can be filed per TurboTax online account.

To create a new TurboTax account, follow the steps below:

https://ttlc.intuit.com/replies/3288574