In the 'Language Settings' panel (accessed as in my first post), you can drag a language to the top of the 'preferred languages' list to make it the first choice for Windows. If you click the 'Keyboard' icon, you can use the drop-down menu to choose between automatically using the first language shown or any of the other languages that you've got installed.
Once you´ve got more than one language installed, press the Windows key and your spacebar together to enable you to choose which one you want to use.