Before I can give any specific advice – can you give more detailed info about the components you are using ? Do you need to backup on an internal or external hard drive ? Have you considered RAID as an option?
Backups can be done manually but this isn't very practical for large amounts of data and/or if it has to be done periodically. If I understand correctly – you may need a software solution, which can do scheduled backups. There are such solutions, like WD SmartWare, among other software. Most of them will enable you to choose from automatic, continuous backup or scheduled backups. You will also be able to back up to a local external hard drive or to a cloud storage.
If your main concern is storage volume and data security – you may also look for a NAS device (Network Attached Storage) with a RAID option, in addition to the backup software.
Waiting for details so I can be more specific, best regards, Citizen_WD