On 12/1/18, I moved from TX to SC for my job in GA. My employer withheld SC taxes for Dec. How do I file my SC and GA taxes?

You do not need to file a return for Georgia in 2018. You did not live there. You worked there, but the employer withheld taxes for you in your state of residence(SC). You will need to file a part-year resident return for South Carolina. See below for part-year instructions.

https://ttlc.intuit.com/replies/3302008