What do I install

I am just starting out, I downloaded Aptana studio and installed it with the RoR plugin, do I also need the InstantRails 2.0? If so is there a document that relates how to make the Aptana file work with the InstantRails.

You need to download Ruby 1.8.6 and install it. Install rubygems unless you used ruby windows installer. Then fire up console and execute 'gem install rails'. The last thing you need to do is choose correct ruby interpreter in aptana properties. I'm not sure how to do that since i haven't used aptana for long time.