You'll enter interest paid from your bank by clicking on Federal Taxes, then Wages & Income, then scroll down to Interest & Dividends and click on Interest on 1099-INT. Click start and follow the prompts.
TurboTax will ask if you received interest and you'll say "yes." Then click "I'll type it in myself" and you'll be shown a screen to enter your amount(s). TurboTax will address you as if you received a 1099-INT, but you may not have received the form, which is okay. You'll simply type the amount of interest into box 1 on the screen.