UPDATE: this post explains how to install tor on a server if you are using a desktop I suggest yout to follow the how to install tor on ubuntu desktop tutorial instead.

Installing tor, as any other service, on ubuntu is a matter of apt-get. Just type in a terminal:

sudo apt-get install tor

It will install tor and polipo so u are ready to go with tor. But to make everything work u still need to modify the configurations files a bit. For polipo just edit /etc/polipo/config and modify these two lines:

#socksParentProxy = “localhost:9050″
#socksProxyType = socks5

into

socksParentProxy = “localhost:9050″
socksProxyType = socks5

So it’s just uncommenting the two lines. Tor should be already working without any trouble, but it may be slow and u are not contributing to the Tor network. I highly suggest u to configure tor such that u can share your bandwidth with the network.
For changing this u have to modify /etc/tor/torrc and change these two lines:

#ORPort 9001
#DirPort 9030

into

ORPort 9001
DirPort 9030

It’s like in polipo u have to just uncomment them. That’s it! just configure your browser to use localhost:8123 as a proxy and visit torcheck. Congratz! u are using Tor now