ALSA stand for the Advanced Linux Sound Architecture provides audio and MIDI functionality to the Linux operating system. See the ALSA homepage for more information.
See Section 1.3 to know how to build a Linux kernel with ALSA support.
Once you have rebuilt your kernel, install alsa-base and alsa-utils packages. Then as root user execute alsaconf.
Choose your soundcard driver. Alsaconf will set up your system to load this driver at boot.
Next execute alsamixer to suit your needs. However your hardware must contain conventionnal mixer. If not, try to find specific Free projects that support your card (see Section 184.108.40.206).