C:/ had 200GB D:/ has 1TB??

I just bought a new acer computer, it said it had 1TB HD space. I start downloading games from steam when it notifies me there is no space on C:/, which confused me because it said it had 1TB. When I look at the My Computer to see what was going on, it says that my C:/ only has 200 GB While my D:/ has my 1TB. How do I make my D:/ my primary Hard Drive to where all my files I download and things like that will be put onto that drive instead of the C:/? (PLEASE TALK IN SIMPLE TERMS)

Submitted May 30, 2017 at 12:51PM by SilentUMad http://ift.tt/2sglrQ7