My company has provided a test environment for me to learn the Oracle Financial modules. When I login to the application, I don't find anything related to General Ledger. While I was digging the options, I found some ledgers related to Vision enterprise. But, I am unable to find GL Super User or any other reference to the GL module from the Oracle E-business suite home page.

How do we know which modules were installed?? and Is there a way to figure out the different modules installed ?

In EBS all the modules are installed always, no matter we use them or not.
You need to assign GL Super User responsbility to your username.
If you take the tutorials in sequence I have explained each step in the order.