How do i turn up the volume on my sony Vaio with the keyboard?

[J]

theres buttons that show volume on f3 and f4 but when i click them they dont do anything how do i get these to work so when i wanna change volume i can just press F3 or F4 instead of clicking the volume button on the lower right of the screen.

 

[Dennyv4]

You have to hold Fn while pressing F3 or F4 for them to work.