How do I add a line to my /etc/apt/sources.list?

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http://askubuntu.com – I am updating my Tor on Ubuntu and it states: Do not use the packages in Ubuntu's universe. You'll need to set up our package repository before you can fetch Tor. It then states that I have to add this line to your /etc/apt/sources.list file: deb http://deb.torproject.org/torproject.org <precise> main I am uncertain how to add a line to /etc/apt/sources.list. (HowTos)