Your SSD contains everything except your media (OS | Programs | Games) (Certainly not your internet Cache, right?) But you don’t want to store your media (music, videos, photos, downloads, etc) on the SSD, this is how you reassign the default locations of things.
On your HDD, let’s call it “D:\” Make the following folders:
Then go into your explorer and go into your default folders (usually your full name)
It should look like this:
RIGHT click each of the folders, and go to PROPERTIES, and on the LOCATION tab, you will see this:
Change the default location for each folder to the new folder you created on “D”. For example this is for desktop (D:\Desktop) in the image above.
It will ask you if you want to MOVE all the files in there, say yes.
Now you are remapped proper.
While you are setting up your new computer, you might as well continue and setup your Windows 10 Install proper here.