More information:
Depending on your child's overall tax situation, they may not be required to file a return at all. See this web site first. Remember that FFA is "other income" or "other unearned income" and not business income.
https://www.irs.gov/help/ita/do-i-need-to-file-a-tax-return
Second, Turbotax may want to upgrade out of the free version to report other income. As long as the child's income is less than $39,000, you can use the IRS FreeFile version, but you have to make a new account for the child and start over since it is a separate web site.
https://freefile.intuit.com
Lastly, because this is unearned income, it may subject your child to the "kiddie tax". There's not much you can do about that if it happens. More info is here.
https://ttlc.intuit.com/community/income/help/what-is-the-kiddie-tax/00/25913
