How can change?

I'm not sure how you think that anyone without a degree of psychic ability can answer this question. You have said nothing about what the PC is.

However here is a broad answer to a broad question. Assuming that is is pluggable and has a compatible socket, you unplug the existing one and plug in the new one, taking care to refit any heatsink(s) and/or cooling fans.

Vic
June 2010