In Netbeans you can define a new Java Platform from Tools > Java Platforms. This brings up the platform manager. At this point you can click the "Add Platform" button and browse to the location of the new platform. You will then have multiple platforms set up and you can configure each project to use the appropriate platform.
To add the hibernate library you can go to Tools > libraries and click "New Library". Then browse to the location of the Hibernate jar files.
Each project can then have th enew library added by right-clicking on the libraries link in the project browser and clicking "Add Library".