To schedule system cleans (for example clean the system every Friday at 10am) you will need to manually create CCleaner entries in the Windows Task Scheduler. Please note that in order to do this your user account needs to have Administrative privileges.
That’s it. All done.
Note: These instructions are intended for Windows Vista and onwards. On older operating systems this is done in similar way but there are some differences (for example Task Scheduler is in different location).