Synaptic is a GTK based graphical interface to the Debian APT package management system. It provides the same functionality as the aptitude or apt-get utilities and more. Synaptic enables you to install, upgrade and remove software packages in a user friendly way. This may be the package management tool of choice for those who prefer a graphical user interface over using a command line.
Run synaptic from your Applications menu:
Administration-> Synaptic Package Manager
You will be asked for an administrator password.
Installing, removing packages
Synaptic shows you all the packages available to you - and marks each one as installed or not installed. A green check box means the package is already installed. A blank checkbox means the package is not installed.
To find a package, use the search box or Ctrl+F to search packages by name, description, or other keywords; or just browse the package list by category
Mark packages you want to install (or remove) by clicking their check box, or by clicking them with the right mouse button and selecting Mark for Installation/Removal
Click the Apply button.
You can also decide to select Mark Recommended/Suggested for Installation to install recommended/suggested packages which may provide additional functionality for to the main package.
This file can also be edited from synaptic. In the menu, click Settings -> Repositories
From there you can manage Apt repositories type, URL, distribution and components, which affect what packages are available to you, and the system upgrade policy.
Upgrading all packages
Updated packages (minor upgrades or security upgrades) are regularly added to Debian repositories.
If no automatic upgrade mechanism is configured, you can use synaptic to keep your packages up to date:
Click on Update to download new package information
Click on Mark all upgrades
Review the list to make sure these are upgrades you are comfortable with, then click OK
Click Apply then OK to upgrade all packages to latest versions
Upgrading your distribution
See How to release upgrade your distribution to upgrade from one stable release to the next.