In the tools,
menu selects the “Internet Options” line to open the settings.
In the settings, window chooses the connections tab and click on LAN settings for the proxy port configuration.
Now set the check at “use a proxy server for your LAN” and at the “Bypass proxy server for local addresses”.
With a click on Advanced-button, you open the window to open the ports.
Enter the values like on the picture, IP 127.0.0.1 and port 4444 for HTTP, port 4445 for HTTPS.
With clicks on OK, you save the settings and your browser is set to use the I2P proxy.
Note/Privacy tip: Set the FTP proxy to the same settings as the HTTP proxy.