On the input screen for Overpayment applied from 2018, you will see two columns.  One for FEDERAL and the other for STATE.

When you click on the input box for STATE, you will see a + sign.  Click on the + sign, you will see a popup in which you can enter the AMOUNT, STATE, and SOURCE - always select "S" for SOURCE so that it is counted only toward one state.  When you are done making the entries for the first line, a new line will be shown and you can make your entries there for the second state.