graph - Neo4J indexing how to -

I'm new to graphdb and Neo4J, so I do not want this to be a great start to buying your new graph DB Book , But has been very disappointed because I can not walk along in the book too.

The problem is that I do not understand indexing, how it works and does not even explain, for example (Charlie 'username:' Charlie '}), (davina {}): This code:

  create (Alice {username: 'Alice'}), (Bob {user name: 'Bob'}) Username: 'Davina'}), (Edward {user} Name: 'Edward'}), (Alice) - [: ALIAS_OF] - & gt; (Bob);   
 And when I type in:  
  start bob = node: user (user name = 'bob'), charlie = node: user ( User Name = 'Charlie'), Davina = Node: User (User Name = 'Davina'), Edward = Node: User (User Name = 'Edward') Create (Bob) - [: Emmil] - & gt; (Charlie), (Bob) - [: CC] -> (Davina), (Bob) - [: BCC] - & gt; (Edward)   
 I get the following error: ==> Wrong index expiry: index  user  is not present  
 Will someone tell me how I index "user"  
 
 
 
 NEO 4j uses an inverted pointer by Lusen as default. Knowing this will help you understand better. I wrote a blog for this  
 Now, the problem with your inquiry is that you are asking Neo4j for searching  Bob  in the  user   Username . To work for this, you need to enable it or programmatically control it.