From the ALSA wiki
Change to root.
Open the file with your favorite text editor.
If your kernel is 2.4 based:
If your kernel is 2.6 based:
Copy the above text to the bottom of the file by highlighting it with your mouse and paste it by clicking in the appropriate spot with your middle mouse button. If you don't have a middle mouse button then you can press the left and right button at the same time.
If you use the above text editor you will need to put the cursor in the correct place and type: a, which allows you to write to the file. Then save the file. If you use the above text editor type:
ESC shift+q then type :wq! and press enter.
While you are editing the file don't forget to change the sound card to match your hardware. I have a sound blaster live card so I changed these lines:
# ALSA portion alias char-major-116 snd alias snd-card-0 snd-ad1816a options snd-ad1816a
# ALSA portion alias char-major-116 snd alias snd-card-0 snd-emu10k1 #options snd-emu10k1
Notice that I commented out the options line. I don't have any options right now.