With the most recent commit of Yalu102-beta6 Luca has removed support for WiFi and network SSH but kept USB available, this was due to ease of use for people and makes changing your root password irrelevant.
So for now what you can do if you know how to SSH into your phone with USB then you're set but if you don't then follow these instructions.
- Disable WiFi on your device.
- Download iFunBox from here and install it: http://www.i-funbox.com/en_download.html
- Download PuTTY from here: https://goo.gl/13f4zG
- Connect your device to your PC via USB Cable
- Open iFunBox, check to see if your device appears as connected proceed to click on the 'Quick Toolbox' tab, then click on 'USB Tunnel' option.
- Open PuTTY and enter 127.0.0.1 for Host Name and leave the port to 22 then click 'Open'
- When prompted for username enter "root"
- Then you'll be prompted for the password, the default is "alpine" if you've changed that then you can use your own, imput the password and open the connection.
And that's it, I'll update this thread if anything changes but as of now this is one of the easiest methods.