From MEPIS Documentation Wiki
This frontend for wpa_supplicant allows you to query status, change config, and trigger events.
Download and install wpa_gui through Synaptic or using apt-get. Make sure you have already set up wpa_supplicant.conf as described in WPA. As root, enter "wpa_gui" to start the application, which will immediately attempt to connect to the access point using the parameters you set in the config file.