Hi there Jack,
As the other guys suggested, you can use it for storing data as well as backing up the stuff that is already on your computer.
You can either drag and drop it, or use the back up tools that come with the drive. (WD Backup – different back up plans)
Also, you can check the drive's health status with WD's Data Lifeguard Diagnostic tool. (both short and extended DLG tests)
Keep in mind that you should always store your most important data on at least two places.
You can find the tools on WD's website under the downloads section.
It's a portable hard drive and the best thing you could do with it is first virus scan your PC run malware bytes and defragment.
Then create a full system image on the passport drive and then if you ever get infected by a virus or ransomware you can safely erase your whole computer and put it back just like it was easy!
Use it to backup your important files….