Question

how to change bios?

Answer 1

Do you mean adjust the settings or modify the BIOS firmware itself?

Answer 2

Or in some systems, change the chip!

Answer 3

if you asking how to access it, its either the del., esc., or f12 button before the system boots up. Not all systems are the same.

Answer 4

@xbrunomk Some BIOS access keys I have seen:
F1
F2
shift-F2
F10
F12
del
esc
shift-alt-del

I may have forgotten some.

Most machines I press F1, F2, F10, F12, and Delete all at the same time and repeatedly. Usually gets me right in without having to try and read what it says I need to press.