You need to sign on Oracle Technology Network in order to down its database software for this class.  Please note:

1. The university had paid the license for us to use Oracle database for our class.  You need to simply agree upon the terms. 
2. You need to decide the correct version based upon your hardware and operating system.
3. Oracle provides an extensive array of documentation.  As a database professional, you should always review carefully on its administrator's guide (or installation guide) before starting installing your software.  This will help reduce the down time to minimum for your company.
4. Follow the instructions to download.

Have fun.