We use at work; Good Luck!
[actually it’s been a boon saving huge amounts of labour]
I recall there are a couple of ways to use it
1. Design some classes you want persisted in MySQL, perhaps in a UML tool, exporting them to Java get it to auto-gen and it will then deal with it
2. Design a database you want Java access to, perhaps in a UML tool, exporting it to SQL, stuff in your MySQL db then get Hibernate to gen the Java library. Tada you have a Java DAO!
I prefer option 2 because it encourages a better information model which tends to pay off in the long run.
Watch out for exception handling. Had prbs getting it to reliably tell when it’s lost DB connection.