You can't access this because paying student loans is not an exemption that the IRS allows, unfortunately. Yes, the interest is exempt if it was to pay higher education expenses, but the definition of education expenses includes tuition and fees, NOT student loan.
For more information, please refer to Who Can Cash in Bonds Tax Free.
But - just to be technical, when you enter 1099-INT information, TurboTax will ask Did you use your U.S. savings bonds to pay for higher education expenses. You will be able to to continue through the qualifying questions.