Aptitude is preferred, but other approaches can be used if desired.

First, update the package index. The package index is essentially a database of available packages from the repositories defined in the /etc/apt/sources.list file and in the /etc/apt/sources.list.d directory.

sudo aptitude update

Now install the package.

sudo aptitude install package_name

NOTE:APT keeps a copy of each downloaded .deb file in the directory /var/cache/apt/archives/. In case of frequent updates, this directory can quickly take a lot of disk space with several versions of each package.