How to setup URL to rails application

I just installed a rails app - RadiantCMS at a shared host and
realized that the rails app assumes that it operates of out the base
URL, www.domain.com, rather than the symlinked path, www.domain.com/symlink.

Is there some setting to pass for the application to know to add
symlink to the relative URLs.

Its my first trial at a shared host and I am completely caught out?