I assume you mean, how do I control the different audio mixer settings offered by the soundcard, you need to install a mixer application, in this case the "gnome-alsamixer":

Start > Applications > Administration > Synaptic Package Manager > [Type in password if requested] > Search > Type in gnome-alsamixer > Search > Check mark in box "gnome-alsamixer" > Apply > Apply > [wait for it to download and install ] > [when done] "file" > "quit"

Now how to USE the Volume Control... Click:

Start > Applications > Sound & Video > GNOME ALSA mixer