You can replace the hard drive with a 2.5" SATA SSD, yes.  There is no option for adding a drive -- no M.2 socket, nor a second SSD slot, so the drive has to be replaced.

Hi DHOLOMXTC15-19,

Adding to,

You could contact our sales team here and order the SSD - http://dell.to/MTTc4z

Alternatively, find the link for compatible SSD's from Crucial here - http://bit.ly/2hUb3LZ

Also, please click my DELL-username and write me a private conversation with the service tag and your contact details(Name and Email) for case records.

Let us know if you have any other queries.

Yes, you can. Just follow these instructions : www.laptopultra.com/.../

then you would make it :)