Default how to update ATT Samsung S4 to 4.3 OS on AIO network?

Hi recently got on aio network with an att Samsung S4 that runs on 4.2.2. I want to update the software to 4.3 since I am on aio I am not getting the OTA software update. Can someone help me or tell me how can I get a software update that wont crash my phone. I dont know much about how this is done and can someone please help me. Thank you.