su does not change prompt to #
You have to unlock the bootloader first. Here is a page to help you do it: 

https://developer.android.com/wear/preview/downloads.html

Here are step by step instructions:

http://forum.xda-developers.com/watch-urbane/development/everything-urbane-root-how-tos-files-t3243975

That page also contains the files you need to flash.

IF YOU ARE NEW TO THIS PLEASE READ THE POST ENTIRELY BEFORE TRYING TO FLASH OR INSTALL ANYTHING. I TAKE NO RESPONSIBILITY FOR ANYTHING YOU DO TO YOUR DEVICE.