Whenever you download something to install, it will ask for where it will be installed, just redirect the path to your HDD, it will install/store on your HDD.
Alright. Is there anything else I can do to reduce what's already on the SSD? For example, everything that I download off of the Windows App Store just goes straight to a mysterious location, presumably on the SSD. Would moving over the Program Files and x86 folders from SSD to HDD help, or no?