To install a package you can
locate the package you wish to install in konqueror, drag it onto a running copy of KPackage
click on a package file in konqueror and start a new copy of KPackage
use on the Open menu items in KPackage
selecting an available package in the package tree
For a selected package, using the buttons in the right panel, the Examine button will open the package file (fetching it from a remote source if necessary) and display install options and package information.
For marked packages, using the buttons in the left panel, the Install Marked button pops 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 and BSD packages external programs are called. With Debian packages the DPKG utility is invoked in an XTERM window (this allows interaction if required).