In Ubuntu regular version, we use Ubuntu Software Center (USC for short) to install applications. In Kubuntu (Ubuntu KDE version), we use Muon Discover (Muon for short). USC and Muon are two same functional things, but with different details. While USC created specially for Ubuntu, Muon created for any Debian-based distribution using KDE, thus Kubuntu uses Muon. For those don't know, Muon Discover as desktop application is similar with Google Play Store as mobile application in Android, or App Store in iOS, or Mac App Store in OS X. Here, we explain how to use Muon as Kubuntu Software Center.
Before using Muon Discover (Muon), you must do a “Reload” first by performing a command below. This command will download index files from the repository server (so further you can search for any application without internet). If you don't do “Reload”, Muon won't find many apps because it has no index yet.
sudo apt-get update