Browse anonymous websites
To browse anonymous websites inside Invisible Internet, configure your web browser to use HTTP proxy 127.0.0.1:4444 (available by default in i2pd).
In Firefox: Preferences -> Advanced -> Network tab -> Connection Settings -> choose Manual proxy configuration, Enter HTTP proxy 127.0.0.1, Port 4444
In Chromium: run chromium executable with key
Note that if you wish to stay anonymous too you'll need to tune your browser for better privacy. Do your own research, can start here.
Big list of Invisible Internet websites can be found at identiguy.i2p.
Host anonymous website
If you wish to run your own website in Invisible Internet, follow those steps:
1) Run your webserver and find out which host:port it uses (for example, 127.0.0.1:8080).
2) Configure i2pd to create HTTP server tunnel. Put in your ~/.i2pd/tunnels.conf file:
[anon-website] type = http host = 127.0.0.1 port = 8080 keys = anon-website.dat
3) Restart i2pd.
4) Find b32 destination of your website.
Go to webconsole -> I2P tunnels page. Look for Sever tunnels and you will see address like \<long random string>.b32.i2p next to anon-website.
Website is now available in Invisible Internet by visiting this address.
5) (Optional) Register short and memorable .i2p domain on inr.i2p.