You will find the section under the "Your State Returns" section of the program. Select Missouri, and then continue through the questions until you reach "Savings for Tuition Programs". You will answer yes to the question asking "Do you have a Savings for Tuition Program (MOST/529 Plan? account and/or Education Deposit Program account." The next screen will allow you to enter your contribution to the 529 Plan.
I have attached a link which has more details on the Missouri 529 Plan and the amount of the deduction you are entitled to in Missouri. Missouri 529 Plan
I am using TurboTax DeLuxe and do not see anywhere as I go through the screens to enter 529 Contributions in Missouri. Can you clarify your response I am totally confused as I do not find anything asking "Do you have a Savings for Tuition Program? as I go through the Turbo Tax questionnaire for Missouri.
At some point in your Missouri return, you will reach a screen in your Missouri that says Savings for Tuition Programs and this is where you enter the information for a contribution to your 529 plan. It comes right after a screen that says Do You Have Any of These Items Not Taxed by Missouri? It should be there. If you are still having difficulties finding it, you may want to contact a specialist that can work through that section of the return with you.