Enter any amounts you have paid for interest on money you have borrowed for business purposes.
This would include loans for tools, vehicle, etc. This would also include interest you pay on a credit card for business related purchases. A portion of each payment you make is interest.
If you do not know what the amount is, you can ask the financial institution where you have the loan to provide you with an amortization schedule. This shows the principle and interest portion for each payment throughout the length of the loan.
If you cannot get this, let us know what the original amount of the loan was, when the 1st payment was due, how long the loan is for and the interest rate. We will figure the interest for you.