On ubuntu , you can install a package quickly using apt as shown below.
Let us install mutt , the email client. The package name of mutt in the ubuntu repository is "mutt". ( You have to find out the package name somehow)
The following pop will come.
Type apt:mutt in the window as shown.
Click on run.
The following pop up will come. You can press install and the rest of the procedure is same as package install from synaptic.