To apply a portion of your state refund to next years taxes look for the section that deals with calculating estimated payments for 2016. Even if you don't need TurboTax to calculate the ES payments, the option to apply your refund will be within those screens. Each state return is set up a little differently in TurboTax and navigating directly to the section you need varies.
For Wisconsin, the section is toward the very end of your WI tax return. When you come to the 'A few things before we wrap up your state taxes' page under Other Situations click Start next to Handling of Overpayment. (Screenshot attached)