Can't install it!!! Help!

[Sophie Grandsire]

Hi,
Excuse my  poor english. I am french and not fluent in english...
I am trying to install for the first time of my life a free program 
like GnuCash. I had no problem to install Mozilla but here I'm 
completely lost with all the files. I tried to install it in 
Applications , Utilitaries, Terminal but then I got lost...

Is there anybody who could help me with my Mac Os X, 10.4.8 ?

In French, of course it would be easier but I can use a dictionary...

Thanks,

S G-R