How to reset Arduino Yun wifi connection setting?

Hello. I am Arduino Yun user.
I connected Arduino Yun into some wifi access point, but, this AP is very terrible.
so, I want try disconnect.

however, I can not access Arduino Yun.
becuz, Arduino Yun's AP is disabled when connected another wifi access point.

I want try change Arduino Yun's Setting. but, I can not access Arduino.
How can I do?

Sorry my poor english.