To install a package you can
locate the package you wish to install in kfm, drag it onto a running copy of Kpackage
click on a package file in kfm and start a new copy of Kpackage
use on the Open menu items in Kpackage
selecting an uninstalled package in the package tree
In Single select mode the Examine button will open the package file (fetching it from a remote source if necessary) and display install options on the left panel and package information on the right panel.
In Multiple select mode the Install button pop up a dialog of install options, when install is selected in this dialog any remote packages are fetched and then all the selected packages are installed.
RPM packages are handled slightly differently from other package type, RPM packages are installed by the Kpackage program while with Debian, Slackware, BSD and KISS packages external programs are called. With Debian packages the DPKG utility is invoked in a KVT window (this allows interaction if required).