Well first of all don't worry
Matter of fact, you might need the bios when installing the new sound card, but only if you already have an onboard one, for example on your motherboard. If you don't (you have no sound, or you have one already in a slot) then you won't need it.
Anyway, Bios is basically this taken from google define:
"An abbreviation for Basic Input/Output System. On PC-compatible systems, the BIOS is used to perform all necessary functions to properly initialize the system's hardware when power is first applied. The BIOS also controls the boot process, provides low-level input/output routines (hence its name) and (usually) allows the user to modify details of the system's hardware configuration."
You acess it usually by pressing Del at bootup, and it allows you to access loads of settings. Some will do you harm if you don't know what they are though, so don't go tampering
Though if anything was to go wrong and your PC doesn;t boot up because of it, there is actually a way to reset it, but I wouldn't worry about that as yet
I hope this helps