This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
the only thing you have to know additionally to what is said in that tutorial is how to configure and declare a DataSource. This is done using the <resource-ref> tag in the deployment descriptor, for example:
In your program you can then look it up using JNDI. Note that res-ref-name is relative to java:comp/env.
The rest of the configuration depends on the web container or application server.
Note that it is common to use a more abstract persistence API rather than using JNDI directly. Common choices are BMP, Hibernate or a custom DAO implementation.