How do I use my 2TB Internal harddrive with my internal SSD?

Recently bought a new computer, custom build. I have two inteal hard drives and one exteal. I have a Samsung Evo 850 500GB and a Weste Digital BLACK SERIES 2TB 3.5" 7200RPM Inteal Hard Drive. I'm currently booting from the Evo, but I don't know I can use my 2TB hard drive in conjunction, so I can put all my 'useless' data on the 2TB (Pictures, Movies, etc.) HDD and then use the SSD for stuff that matters. Was also going to cut up a small partition of the HDD for a different OS

Thanks, guys!