The latest release (7.0) dropped official support for Rails :( .
However you can continue using it via a community maintained plug-in:
- Install Netbeans from http://netbeans.org/downloads/index.html (I picked PHP distribution since it is the lighter one)
- Add a plugin repository :
- Tools -> Plugins -> Settings
- click 'Add' and write a name (e.g: Beta rails) and a url 'http://updates.netbeans.org/netbeans/updates/7.0/uc/beta/stable/catalog.xml.gz'
- refresh available plugins, filter by 'rails' and install it
- Restart IDE, rescan Ruby platforms:
- Tools -> Ruby Platforms --> Autodetect Platforms
here are some links for more information on NB + Rails: