BIOS is firmware (not software). It is always provided for free from the manufactuer.
BIOS is stored in an EPROM (Eraseable Programmable Read Only Memory) chip on the motherboard. It tells the computer how to do the most basic of things like booting and where to look for hard drives, etc...
If you update the BIOS you must ensure it is done thoroughly and completely and with the CORRECT firmware update. Failure to let the process complete or using the wrong firmware will cause your computer to be brain dead and requires the manufactuer to reprogram the chip.
BIOS updating should be done by an experienced computer user. It is not for newbies or those not willing to risk a dead motherboard. If you are willing to accept the risk and you NEED an update, then its a rather simple process.
BIOS updates are best done via a standard floppy disk drive. This is because BIOS is part of core computing architecture that goes back to the earliest computing days. ALL intel and AMD CPUs have at their very core legacy architecture.
Normally your new BIOS file and BIOS programmer file are on the floppy. You can download them from the manufactuer or get them supplied to you. You boot this floppy drive. Most BIOS programmers will let you save the old BIOS (download it from the EPROM). Always do this and save it to another floppy disc.
Then using the programmer, type the name of the new BIOS you wish to upload.
(specific instructions will vary from motherboard to motherboard.)
BE PATIENT. If you fail to complete the upload process, your system will be brain dead.
It can take a long time sometimes.
As I said before, I do not recommend changing the BIOS unless it is absolutely necessary for compatibility purposes.