Use the supplied "SmartWare" software to set up your backup options on a schedule, but remember to leave your PC running for the backup period you have set. The SmartWare user manual is here: http://www.wdc.com/wdproducts/library/UM/ENG/4779-705057.pdf
@Phillip Corcoran is right, you can use the WD SmartWare that comes with the My Cloud. You can use the link he provided to learn more about the software itself. I can also add up with a couple of links from our KB that explain how to backup to the WD My Cloud and create a scheduled backup using SmartWare.
How to backup a computer on a WD Personal Cloud drive: http://products.wdc.com/support/kb.ashx?id=fDJwDr
How to create a Scheduled Backup with WD SmartWare: http://products.wdc.com/support/kb.ashx?id=JScnXS