How can I add my bank account to see what can be deducted for self-employment work?

Please explain what you are trying to do.   Why do you think adding your bank account will show you what you can deduct for business expenses on a Schedule C?   You can add your banking information in the FILE section for your direct deposit.   You cannot "add" your bank account in order to put in your business expenses.  Those need to be keyed in by hand.

You can't add your bank account. You will need to determine which expenses are for your business and which are personal. See What self-employed expenses can I deduct?  along with the IRS Deducting Expenses.

Several years ago they did have an Expense Finder but that was discontinued.