T3500 extram case fans

Hello!

I am wanting to install a couple of extra case fans in 2 of my T3500s.  Is there something i can look at as to how to get this done.

Should one be exhaust and one intake , i would like to put both on back of the case if thats possible.

Never done this with a delll case only with my orginal builds.

Thanks in advance for your time.