You don't. Income earned from working or performing a service is always reported on a person's own tax return in their own name, even if they are someone else's dependent.
The only time you would report a dependent's income on your own tax return is if the only source of income is unearned (that is to say, investments and other passive income from investments placed in a child's name) below a certain dollar amount.
Note that in Turbotax online, each account can only file one tax return for one person. You will need to make a separate account for a second return. And the second account will charge separate fees, unless you qualify for free filing. If the income from business is less than $36,000, you will want to use the IRS FreeFile edition of Turbotax, since it includes the self-employment forms that regular Turbotax will charge extra for.