If you don't know those pieces of information, I can't help as much...
You need to find out where your Spring configuration files are, usually called applicationContext.xml or something like that. They'll usually live in the src/main/resources directory of your application somewhere, sometimes in there as META-INF/spring, (I'm assuming
Maven here). Did you have SpringSource ToolSuite set it up for you? In that case, that's the directory. If not, did you use Roo? Same place...
The persistence.xml file is where you define your JPA configuration, such as the JPA provider and mapping information. The applicationContext would be using an EntityManagerFactoryBean to create the entity manager, and that's where the JPA config is. Then you'd mount a transaction manager in the same configuration file.
You may need to read up on these things to understand why you're getting the behavior you're seeing - the Spring Framework documentation is quite good, as is Craig Walls' Spring in Action book for example (not a plug, but he goes through these things in great detail).
I suspect you don't have everything wired properly and that's why nothing is being persisted.
If you have Roo build you a JPA-based application, such as running 'script wedding.roo' - you'll see how they organize their configuration, although they use AspectJ for the transaction management, which can make learning from it a tad tricky.
Ken