You need to go to the Federal Taxes section...that's where it is entered.
(or the Personal taxes section if you are using Online SE or Desktop H&B software)
In the Deductions&Credits section. ("I'll choose what I work on"...don't use the "Guide Me" )
Scroll down to the Estimates and Other Taxes Paid section..
...go in on the "Other Income Taxes " line
look for the "2017 refund applied to 2018 state taxes" line....Start there.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*