Installing and managing software on Fedora Core 15 is very easy.

Installing packages. yum install <PACKAGE>.

Upgrade a package. yum upgrade <PACKAGE>.

Uninstall a package. yum remove <PACKAGE>.

You may also use the rpm command to install an RPM package that you have downloaded off the Internet.

rpm -ivh <PACKAGE> To install a rpm package.
rpm -Uvh <PACKAGE> To upgrade an installed rpm package.
rpm -e <PACKAGE> This will remove an installed package.
rpm -q <PACKAGE>. To query the version of an installed package.
rpm -ql <PACKAGE>. To list all the files installed by an RPM package.

Sometimes when installing a rpm package you have downloaded from the Internet there are unmet dependencies. In this case you will need to source the required RPM packages and then try the installation again. if you create a folder containing all the required RPM packages, then you could type rpm -ivh *.rpm and they will all be installed. The below image shows the KPackageKit package manager GUI with packages selected for installation. You can see the packages I have selected for installation.

The Xmms multimedia player is a very old and very good music player and I am adding Modplug and AAC plugins for that music player to enhance the application. The Gnome package manager is very similar and just as easy to use as the KDE package manager. You just type the name of the package you are after and click find.