From where I can able to see UI code of ManagaeIQ?

I want to explore source code of ManageIQ. I am able to find UI code in ManageIQ-ui-classic repository but I am not getting it in container of manageIQ installed on my machine(ManageIQ-hammer2). So please help me in understanding where is actual UI code and why I am unable to find it in container of ManageIQ.

The UI code is installed as a gem the main ManageIQ application depends on.
If you just want to view it, it should be in the GEMPATH.
If you want to develop for it, there is a developer guide on the manageiq homepage

okay Thanks

If I want to change UI and add new item in navigation bar then are there any changes required to do in Gemfile.
Another question is do I need to create own plugin to achieve this.
And how to update docker image so that I can check whether new code changes are working or not.