As said by the Dmitry you can created new class library project in which you have to create new public class with you logic for that task.
This all are lies in the CMSApp solution not in MVC solution.
And then in Admin panel(CMS) follow below steps.
1 - Create new task in "Scheduled tasks" application.
2 - In task provider give your generated class library project name.
3 - Select the logic class file from that project below this text box.
4 - Set your schedule in period from (second,minute,hour,weekly etc).
5 - Also can schedule by the days and time.
Hope it will gives you brief idea about how to set the task.