The ZoneFlex Solo AP User Guide has instructions on how to configure security on your WLANs.
https://support.ruckuswireless.com/documents/1137-zoneflex-indoor-ap-104-0-user-guide See the section titled: Configuring Wireless # (WLAN Number) Settings, starting on page 104.
If you mean changing the Admin password to access the AP, see the section titled: Changing the
Administrative Login Settings, starting on page 133.