[CentOS] Using YUM

I haven't configured YUM .

How do I do it?
Sorry if this is a really stupid question, but I have no idea about it.
Moreover, I would also like to use APT afterwards.

I really want to try both of these.
I have used apt-get before many a times, but never used YUM.

Can anybody post the procedure to get this working?
Which repositories to be added, how it is to be configured?

And yes, how do i use the apt-get on Cent OS too.

Note that I will be using only one at a time. And I will keep the
other thing for future reference.


Thank you.
-- 
"No-one dies a virgin. Life screws everyone."