Can anyone help me making ah Case Diagram for Online enrollment? can anyone provide links to a good Case diagram tutorial? and Please help me here

i only glanced at this but it looks quite solid for a starting point.

Use case diagrams should how the system and not how the system will react to the user's input e.g. the some use cases for a cash machine will be enter card, enter pin, request cash, recieve cash, recieve card.

hope this helps