The scheduler is a portlet that can be added. It is located under CMS Administration in the personalize pages. It can be used to write Java classes that can be scheduled to run. These Java classes are Quartz classes and need to implement org.quartz.Job interface. Once you have your Job class you can upload it and schedule it.
To add a job you click on add new user jobs
You may use any name and description you like but the class needs to be teh fully qualified name of the job. You need to have your job on dotCMS classpath first. You can jar it up and place it in common/lib/ext of place your class under dotCMS/WEB-INF/classes.
Select your times to execute and save.