Synaptic Package Manager: Click Reload to refresh the repository data, and Mark All Upgrades to keep all your installed software up to date.
To search for an application in Synaptic either click "EDIT > Search" or use the keyboard shortcut CTRL+F. you can search by description, name, version and many other methods. Type in keywords like "mp3" or "DVD".
Adding new software is as simple as right clicking on a program you want to install and clicking "Mark for Installation". Synaptic will gather the dependencies and add it to the list of things to do when you click "Apply"
After you've selected a package You'll see synaptic has marked your changes in the left column.
Before Synaptic Starts processing your Changes, it will ask you to confirm what software to add, remove or upgrade.
Synaptic Downloading New Software Packages
After Synaptic has gathered all the software packages (called .deb files), it unpacks them and installs them. Click "Show Details" to see what it's doing.