A:Answer You have a choice. You can either replace the original hard drive (actually a M.2 SSD), or you can add a new hard drive or SSD (solid state drive) into the empty bay that is inside the laptop. If you put a new drive into the empty bay, you will have 2 storage units in your computer, which is really nice. The laptop came with a tiny cable and some screws to mount the new hard drive or SSD into the empty bay.
In my case I purchased a Western Digital 1-terabyte (1TB) SSD (Model WDS100T2B0A) to put into the empty bay, and it works fine. I recommend Western Digital drives because of their reliability in general. Some other brands of SSDs have higher failure rates. Ii purchased the drive from Amazon for about $118. I usually stick wiith the Western Digital "Blue" drives for everyday use. Their 'Black' drives are for very heavy users and are more expensive, and their 'Green' drives are too slow.
You can download the Upgrade Drive for your computer from the ASUS website. It will show you how to remove the cover, etc.
I hope this helps with your project.