webMAN MOD is launched automatically by "boot_plugins.txt".
It looks like you are launching the installer, which restart the console when you start it. After reboot, the plugin is loaded by Cobra and the plugin starts to scan the content on your storage devices. When it completes, the games found are listed under "webMAN Games" menu on "Games" column.
After the installation you can delete the installer and continue using the plugin through "webMAN Games" or the other interfaces (sLaunch Menu, VSH Menu, internet browser, etc.)
If the plugin is correctly installed and running, press "SELECT+START" and you should see a notification message showing some system information.