TurboTax wants me to submit information for boxes 15-20, however, those boxes are empty on my W2. What should I do?

If those boxes are blank on your W2, for that question (see screenshot), say No.

I am using the deluxe online version. Boxes 15-20 are blank, I live in Florida. It will not allow me to type in no.

Just make sure you leave them all blank and don't have any spaces in them.  Try backspacing in them.  

Or try deleting the W2 and re enter it.