If you are starting up in KDE (and the systray is on the taskbar), there is probably a little picture of a German Flag. Click on that until it changes into an American flag and that should be all you need to do.

Otherwise (still relatively new to KDE so bear with me), in the configuration menu (icon looks like a computer PCI card), I believe there is a KDE setup wizard that will allow you to set language, etc.

Hope this is of some help,

Joe