I live in Kansas but work part time in Oklahoma for my company based in Kansas. Why is the income I earned in Oklahoma showing up on my Kansas Income Tax Return?

Your resident state taxes everything you make no matter where you make it .... so you need to complete a non resident OK return FIRST  so that you will get a credit for the taxes paid in OK are a credit on the KS return so you are not double taxed.  

Thank you for your answer. How do I check on TurboTax to ensure I am getting that credit?

Line 13 : <a rel="nofollow" target="_blank" href="https://www.ksrevenue.org/pdf/k-4018.pdf">https://www.ksrevenue.org/pdf/k-4018.pdf</a>