Desktop Installs

[Tom]

I cannot install programs from the desktop environment. I download to
the desks top and unzip the programs (mostly tar.gz) and it creates a
folder on the desktop w/ install file in it. I then go to terminal and
do the sudo apt-get install and the install builds a directory tree then
gives error message: couldn't find package or file. I was working from
the tom at tom-desktop$ prompt. What am I not doing right??

Thanks,

Tom