How to include child's Capital losses In your Tax return

It depends, the way to file taxes for unearned income(Form 1099-DIV and Form 1099-INT) for children is determined by how much they've made. 

• If your child's only income is unearned and doesn't exceed $1,150, it doesn't need to be reported
• If your child's unearned income is between $1,150 and $12,950, they may need to file their return, but in certain situations, this income can be included on your return
• If your child's unearned income is $12,950 or more, they need to file their return

TurboTax will guide you through the steps of the process. 

1. Open or continue your return
2. Search for child income and select the Jump to link
3. Answer Yes to both Any Child's Income? and Child Required to File?
4. Select Continue on the Reporting Your Child's Income screen
5. We'll ask you a series of questions to determine if the income can be included on your return or if your child needs to file their own return

But, the exception to this is If the income includes a 1099-B, sale of securities. This needs to go on a separate tax return for the child.

Here is a TurboTax Help article with instructions for entering a 1099-B.