How to Install Maxima on iMac?



Hi, I'm Alessandro. I'm really intrested in Maxima.
First because it's an open source software, second because it's what I was
looking for.
I'm a neo Mac-user. I downloaded the file maxima-x.y.z.tar.gz
I unpacked the folder on my iMac (Leopard is installed)
but I can't run the software Maxima.

I need a list of instructions to do this because I'm not so good with Mac
and I don't know how to go on.

Please if somebody could help me, I would be really pleased. Thank you very
much.