There's a waiting room on the south exit side, and that's where it is.
There's a notice on the entrance about the hours of use, stating 8:10 AM to 6:50 PM. However, it also says that it can't be used during the late night and early morning hours when trains aren't running (10:30 PM to 5:30 AM). It's unclear whether it can be used from 5:30 AM to 8:10 AM and from 6:50 PM to 10:30 PM.
It's possible that 8:10 AM to 6:50 PM is the tentative usage time.