It's located at the roadside and very near "Bangseo intersection".
Walk 100m towads "Air Force Academy" from "Bangseo intersection" then you will see on your left.
I recommand to take a taxi and show the address("방서동 206-1" or "방서동 대머리해장국 옆").
Cheongju is small city. You can go anywhere with less than 10,000 won.
This gym is located near Sannam-dong, Bumpyeong-dong, Youngam-dong, Geumcheon-dong , Youngum-dong and Sugok-dong.