The $10 credit will be automatically applied to the first thing you pay for. Like for the state efile fee or the additional state program. You will get it on something. So when you buy the second state program it should show up. Currently the extra state is $45. And there is a $25 state efile fee (including for the first state) but NY is free to efile.
https://turbotax.intuit.com/desktop-pricing/
