If my son worked where can I add Jagger's income of $406.78 he earned, where do I enter this income on these tax return?

Go to Personal > Personal Income > Less Common Income 

This is at the bottom of the personal income section

If the income is earned from a job, you likely do not need to enter his income on your tax return.  See Do I need to file my own taxes if I'm a dependent? and Do I need to file a federal return this year? to see if his income needs to be reported.

@CC510

You probablu don't need to do anything unless they withheld taxes. He didn;t make enough to file and you don't need to include in your return. If they withheld income taxes you can get them refunded by filing but the cost of turbo tax is probably more than the refund.