The Brightbox Gem is a set of extensions to the Capistrano deploy recipes that makes it very easy indeed to deploy a Rails application onto a Brightbox.
If you've not used the gem before try out Quick Start Guide
This guide covers version 2.1.1 of the Brightbox gem. Run brightbox -v to see whether you need to upgrade.
Instructions for using the older Brightbox gem (using Capistrano 1.4.x)