How to apply for a new J1 visa?

Hi,

I am a research scholar with J1 visa. Due to the need of program, I have already extend the visiting date and got a new DS2019 with expired date 31 Mar. 2020 from my university sponsor. The original expire date on my visa is 19 Sep. 2019 but I need to back to China on Oct. So I'm wondering how can I also extend the expire date on my J1 visa? Thanks so much.