Im a PA resident, worked in MD for 6 months last year and they only withheld MD taxes. How do I file a non resident MD return on here when I am doing my Federal/state?

Yes, you are correct.  You will have to file a nonresident MD (Form 505NR) tax return to get your refund and a resident tax return for PA.  

If you've already entered your personal information, review your entries to help ensure that TurboTax will help you create the correct nonresident tax return.

1. Launch TurboTax and select My Info
2. A Personal profile summary screen will pop up
3. Select Edit by your name
4. Scroll through the screens to ensure that you have the correct answers for your state of residence.
5. Scroll down to Other State Income and select Edit
6. Check your answer for Did you make money in any other states? Answer Yes, and indicate that you made money in MD.

After you complete your federal tax return and you move to the State Taxes sections, both your non-resident (MD) and resident (PA) state returns will be listed.  Prepare your nonresident tax return first.

For additional information, refer to the TurboTax Help articles Do I have to file tax returns in more than one state?,  Why would I have to file a nonresident state return? and How do I file a nonresident state return?