For my state taxes it’s showing that I owe over 600 dollars. But I am active duty military, my military pay is tax free in Pennsylvania. How can I amend my return?

You do need to file a resident return for PA.  You would exclude your military pay.  You must send in a copy of your W2 and PCS orders showing your move to CA  as proof that your active duty military income was earned outside of PA.  Here is a link with instructions to send in the documents when e-filing your returns.  Here is the PA tax reference.  All other pay is taxable to PA as a resident.  

When you enter your military W2 information be sure to check the box for "Active Duty Military Pay" in the follow on questions.  Be sure you have selected PA as your resident state in "My Info" and indicate that that you did not live in any other state.  

Edit your PA return in the state interview.  Select "Update" for the "Income and Adjustments" section. The military pay should be excluded on the "Compensation Summary" page, but if not, you can edit and exclude it yourself there. 

For CA your military pay is not taxable since you are a nonresident. If military pay is your only pay you do not need to file in CA.  If you have other pay you will file nonresident CA for that income.  You can get a credit on your PA return for taxes paid to CA on that income.