My brother forgot to file taxes for his other job aswell, how can he file for that other job aswel?

He can amend his return, after his initial return is accepted and processed.  To amend a return  into TurboTax.com or open your TurboTax software installed on your computer. 

Select the option “Amend a return that was filed and accepted.” and add-in the missing information.  

You can see more detailed instructions on the amendment process here: How to amend a return in TurboTax.