commandline

About apt-get 

http://doc.ubuntu-fr.org/apt-get 

http://askubuntu.com/questions/222348/what-does-sudo-apt-get-update-do

About Upgrading

 Upgrading

su

(password)

apt-get update

apt-get dist-upgrade (or apt-get upgrade)

exit 

 About Wget

Wget is an open-source commandline tool for downloading files using HTTP. Wget is licensed under the GPL license. Wget enables you to download any file instantly to your current working directory, all you need to do is provide the URL.
Example:

sudo wget http://downloads.slimdevices.com/nightly/7.8/sc/89c295b/logitechmediaserver_7.8.1~1406278657_all.deb 

sudo dpkg -i logitechmediaserver_7.8.1~1406278657_all.deb