If you open Task Manager, click on Performance tab and on Memory, it will tell you your total RAM and how many slots are in use. Yes, you may have up to 64 GB (two x 32 GB). Crucial RAM is a good choice because it is guaranteed to be compatible and you can return it if it doesn't work in your laptop. This page at Crucial shows you exactly what type of RAM to order. Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. I know many people do such work without this, but it's a cheap and sensible precaution.
I want to upgrade my ram , I think I currently have 2 8GB sticks total of 16 gb installed.  Does XPS 15 9510 support 64 gb ram if I buy 2 32gb sticks? Also is there any technical detail I need to look for for compatibility?  I believe I need 3200mhz SODIMM modules, I wonder if there is anything else I need to specifically look for while shopping RAM.  
XPS 15 9510 Ram Upgrade