How can I changue URL in redmine code (ruby on rails)

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Ruby

Rails

First of all sorry for my poor english. It's my first time working with ruby on rails and i don't have so much idea.
I have a redmine proyect mounted in a virtual machine, i can access to it writting my ip an it works.
But the problem is when i want to enter from an external link, (i have my virtual machine on a server)

I have this external link

companyname.com/MyServer/myVirtualMachineName/

And i can access to my proyect, but css doesn't load and all links are bad routed, for example:

companyname.com/login

I need to change it into:

companyname.com/MyServer/myVirtualMachineName/login

How can i change it? thanks for reading me.

What I have tried:

Nothing because i don't know how to begin.

I work with Apache.
Rails 3.2.22 (i can't update it)
ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-linux] (same issue with ruby, i can't update it)