Asp.Net c# subscribe button

How to create a subscribe button (control events, code behind used) in a web application. Please If somebody could help...

Scenario : An online learning environment system, where student view list of courses available. A student subcribes to a course posted by a Tutor. A subscription request is sent to Tutor. Tutor accepts or rejects subscription request. As the tutor accepts the student can download the course materials.

I dont have an idea how to proceed with subcription part. If somebody could help. Thanks in anticipation.