apt-get help upgrading

[brendon]

hi there all, i am running the defult installation of firefox and the 
likes,  but i was wanting to use apt-get to upgrade it to the latest  
and also amsn as well.
is there any command or way i can do this or a repo entry that i can add 
that will have the latest, versions, and yes i could go and download 
them from the websites as well,  but wanting a bit more command 
interface  practice as well, 
thank you using breezy

Brendon Toogood