Where/how do I enter the supporting details for an expense for example I used t be able to list all my utilities expenses and it was totaled up automatically?

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.