Make sure that you have the VitaDeploy app installed
Open the Settings app and navigate to "HENkaku settings"
Tick the "Enable Unsafe Homebrew" box, this is required for VitaDeploy to work properly
Make sure that your console has a working internet connection
Open VitaDeploy and navigate to "Install a different OS"
Click on "Quick 3.65 install"
--- the app will download and install a few packages, then it will start the firmware installer, just wait ---
Follow carefully the instructions displayed by the "modoru" firmware installer
After system software install is complete the console will reboot
You should be now on firmware 3.65 with the "enso" permanent hack as well as some useful homebrew plugins, you can verify it by going to the "System Information" tab in the Settings app