<< I have just bought an Athlon 3200+ cpu to upgrade my PC >> You understand your 3200+ is a socket A & very old indeed.
<< how do I change the settings to get the most out of it? >> Doesn't matter how you tweak the settings ,it'll still be too slow for today's computing standard.
<< Also, can I over-clock it and if so how? >> I doubt the Acer bios will let you do it.