If you are using the TurboTax desktop editions click on Online at the top of the desktop program screen. Click on Download State.
An additional state tax program other than the free state received when using the Deluxe edition or higher is $45.
for the desktop editions once the return is opened go to the online tab and use the download state link. there will be a charge.
for the online editions, click on the State Taxes tab. Click on Your State Returns. Click on the Add Another State button.
also, when in step-by-step mode there should be a question about having income from another state which will allow you to add additional sattes
when doing your return complete the non-resident state (s) before the resident state.