How do I get access to UI for the linux VM I am assigned? Is there a way I can use it form UI rather than just using from terminal window
Cloud9 is built on an Ubuntu Server VM. As such there is no UI other than the Cloud9 interface. If you want a desktop, I would suggest looking at this repo: https://github.com/shadowcodex/c9.ide.desktop, but I believe installing extensions is broken right now, so you may not be able to use it.