How to configure for 2 identical backups on separate drives?

This is what I want to do, the question is how can this be done using the Smartware software.

I have purchased two 4 TB Smartbook Drives to back up my photographs and the intention is to leave one unit at an off-site location and the second unit connected to my home PC.  Once a month I would then bring the off-site unit home and take the one from home to the off-site location.  I would then connect the off-site unit to my home PC and the intent would be that it would add whatever files I created in the past month and continue backing up files for the next month.  Then repeat the process.   Backup process is set to continuous.

I have already populated one of the 4 TB MYBook drives with the data, have disconnected it and now connected the second unit but it is not making any back-up copies to the second drive.

What do I need to do with the software or the second drive to make this work?

Thanks

At this moment WD SmartWare can only store files from your computer, and will not sync external drives to mirror each other. This means you may need a different application to better match your needs.

Regards,