First, create a new Passenger app in the Webfaction control panel. You can create a Rails app, but it adds some extra cruft you don’t need.
Log into the server, and install rbenv locally, using the standard rbenv tutorial. You will want to also install ruby-build in order to set up your ruby versions. Compile and install the desired version of Ruby using
rbenv install 2.2.2 (change the version to match).
I suggest that you update rubygems and install bundler at this point by switching to the desired version of ruby (
rbenv global 2.2.2), and running
gem update --system and
gem install bundler. You may want to switch back to system Ruby, although this is up to you (
rbenv global system).
In the app directory (webapps/yourappname), edit the Nginx config file at
passenger_ruby to be
After a restart, you should be running on your rbenv ruby.