How do I add more expenses that were not transferred from my business account to my tax return?

For self-employment expenses that are reported on Schedule C, follow the instructions in the TurboTax help article Where do I enter my self-employment business expenses, like home office, vehicle mileage, and supplies?

Here are additional resources that will help you as well:  What self-employed expenses can I deduct? and What can I write off as a business expense?