I switched from ubuntu to kubuntu today using apt-get install kubuntu-desktop, which worked fine except from the fact that the login screen that pops up when I boot up my computer is still the unity login screen. Is there any way I can change it? I've been looking for a few hours now and I have no clue... (I'm using 13.10)
Most desktop environments have their own desktop manager (aka login screen) however it typically doesn't auto install along with the desktop environment. Unity uses lightdm, Kde uses kdm, and gnome uses gdm. You can have multiple installed but only 1 can be used at a time. You just need to install KDM and set it as your default desktop manager.
Step 1: Install KDM by typing "sudo apt-get install kdm" in the terminal
Step 2: In your control panel both lightdm and kdm will be listed and allow you to change which is your default. You can also do this via terminal commands but I can't recall them off hand.
[Please note: KDM comes with several themes pre-installed, the default used theme is not the one that is used as default in the offical kubuntu iso, that theme is included in kdm though, so all you will need to do to change it to your default theme is go to your control panel and under kdm you can change themes].