sudo apt-add-repository ppa:i2p-maintainers/i2p
Update your repositories and install i2p:
sudo apt-get update sudo apt-get install i2p
Start the I2P router (never as root):
Configure your browser to connect through I2P. I'd recommend you to use Firefox.
Preferences --> Advanced --> Network tab.
In the Connections section, click on the Settings button. Click the circle next to Manual proxy configuration, enter 127.0.0.1, port 4444 in the HTTP Proxy field. Enter 127.0.0.1, port 4445 in the SSL Proxy field. Add localhost and 127.0.0.1 into the "No Proxy for" box.