A child income is reported in the same way anyone else's is. You would follow the same procedure of filing her return as you do your own. You would indicate that she is being claimed as a dependent in the Personal Info section at the beginning.
Tax filing requirement (for dependents)
The minimum income requiring a dependent to file a federal tax return. 2020 filing requirements for dependents under 65: Earned income of at least $12,400, unearned income (like from investments or trusts) of at least $1,100, or self-employment income over $400.
