I wouldn't try to use KWiFiManager -- Slackware's configuration is really set up to be done from the terminal, and the presence of KWiFiManager is really just there because it came with KDE. It is not set up to properly handle things the 'Slackware way'. If you want to configure a wired connection, run `netconfig` as root. If you want to configure a wireless connection, read
Alien Bob's guide. If you want a graphical solution, you could install wicd (a SlackBuild is available at slackbuilds.org or a prebuilt package from
rworkman's repository). Note that if you do decide to use wicd, you CANNOT use rc.inet1.conf (or any other script in /etc/rc.d/) to configure your wireless networks -- wicd would conflict with the configuration. wicd would be the easy, graphical solution if that's what you're looking for.