Problem with datatable..

HI guys,
i'm a new user of JSF and now i'm descovering great possibilities
offered by datatable.
I read the article on
http://balusc.xs4all.nl/srv/dev-j2p-dat.html#RetrieveAndStoreData,

Not everythings are for me clear...
I've to show in a datatable a mysql table

utenti(firstName,lastName,city)

which its relative values..
i've developed a User class with the tree values as private variables
and getter and setter methods...
For this class i've developed a method called userList() that should
return a List of all the users presents in the table,ordereb by name.
Can someone say me what are the successive steps?Can you help me with a

bit theory about wrapper class?
Can you help me step by step because i don't understand internet
articles and forum discussions?

public List userList() throws Exception {

                        Context ctx = new InitialContext();

                        if (ctx == null) {

                                throw new Exception("Boom - No
Context");

                        }

                        Context envCtx = (Context)
ctx.lookup("java:comp/env");
                        DataSource ds = (DataSource)
ctx.lookup("java:comp/env/MysqlJNDI");
// "java:comp/env/jdbc/nomedb"
                        Connection conn = ds.getConnection();
                        Statement stm = conn.createStatement();
                        ResultSet rst = stm.executeQuery("select * from
utenti order by
username");

                        List users = new ArrayList();
                        while (rst.next()){

users.add(rst.getString("firstname"));
                                users.add(rst.getString("lastname"));
                                users.add(rst.getString("city"));
                                                        }
                        return users;
        }

Please help me....