Nabble isn't available as an installable package at this time. (It used to be on the road map, but I think it's still a long way off.)
To access the source of your own applications simply use the "See how NAML generates this page" link at the bottom of any page. On your own app this is editable. Documentation is at:
http://naml.nabble.com (though it is still a bit thin at the moment.) and there's a special area of the support forum for queries at:
http://nabble-support.1.n2.nabble.com/NAML-Free-Support-f6942073.html
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.