The amount paid to principal is the payment amount minus the interest amount. Like the first line the payment amount is 221.43 and the interest amount is 8.13, so 221.43 - 8.13 is 213.30.
The new principal is the amount of principal minus the amount paid to principal. So in this case: the principal started as 1300 for the first month. So to find the new principal you subtract 1300 - 213.30 and that will give you the new principal.
Then next month you will take the "new principal" amount and multiply that amount by the interest rate to determine how much you will pay in interest that month.