Normally if your using the ubuntu desktop with the gui installed, i would use the ubuntu
software centre to install any programs you are looking for. they have a search feature in
there to find any program your looking for.
If you want to download an individual .deb package from one of the Ubuntu repositories you
can use aptitude.
This will download the .deb but not install it on the system.
First of all define your request
for example you want to install wireshark
apt-get install wireshark
if you want, you can upgrade all packages on your system by
You can find ftp server for debian package after you can get al package
Your question doesn't make any sense.
You rarely downloaded packages directly but if you do then use dpkg -i
Otherwise use apt-get update && apt-get upgrade.