If you are using the KDM to login, a box will be displayed at the center of the screen where you can enter your user name and password. Shutdown and Session (down arrow) menus are displayed at the bottom left of the login box with the date to the right. The Session menu lets you change the desktop interface, like GNOME should it be installed. The Shutdown has entries for Switch User, Restart X Server, Remote Login, Console Login, and Shutdown. The Shutdown entry will open a dialog with selections to either Restart or Turn Off the computer.
Upon entering your user name and password and pressing ENTER or clicking the play icon, your KDE session starts up. The login box displays the login splash screen showing the login progress.
You can change the theme of the login greeter using the Login Manager (System Settings | Advanced | Login Manager). On the theme tab you can download and install new login themes (Get New Themes button), and then select the one you want to use. Click apply to use the new theme. If you want to customize your login background, you can turn off themed greeter on the General tab and then use the Background tab to use your own background image.