look for little sun symbols on a couple of the keys in a different colour (often on the arrow keys or 2 of the numbers) and use those combined with the function key (bottom left, labeled FN or similar)
if you look round the keyboard you will also find volume keys that work the same way and others
Yes as the others say, it will be a function key. he function key is next to the Windows and ctrl key. The brightness keys are F7 and F8 on my Compaq laptop, i dont think they'd vary much.