The form 8615 is part of your dependents return, not yours. To get the form ( since you are on Windows machine ), while in federal portion, click on forms and from drop down list select federal and then look for the form on the list and choose open ---- this will put in the form on your forms used list
The form and instructions for the form are here --> https://www.irs.gov/forms-pubs/about-form-8615