If you are using the CD/Download version of TurboTax, you can right-click on most numeric fields and select Add supporting details. A Supporting Details window will pop up for your to add the details. TurboTax will take the total and transfer it to the field on the main screen. [See screenshots below.]
Supporting details screens are not available in TurboTax online. However, you can click the plus sign (+) to Add another row to add more detail.