The most up-to-date documentation can always be viewed in the application itself by clicking on
“Help” -> “The KWiFiManager handbook”
or viewed online in various languages and for various versions at the docs.kde.org website. KWiFiManager is located within the “kdenetwork” section.
Issue #52 of the Linux Magazine contains a three-page article covering the use of KWiFiManager. The really good news is that they have put the article online for free. They have tested the KDE 3.4 CVS version, which means that they don't suffer of the "configuration not saving" bug in their article.