Help with getting bootcamp

Yesterday I bought a game on steam, hoping to play in on parallels. I was not able to do so as parallels does not support directx 11.

I heard that bootcamp does: so I want to get it. The only problem is I am unable to because I am having trouble obtaining this Windows Installer disc, or whatever it is called. I am only able to find a Windows 8 disc but it costs $120, which I am not willing to spend. I tried to find a Windows 7 version but was not successful. I could not find a windows 8 version that was cheaper.

Is there any way I could use my windows version from parallels to install bootcamp? Or is there something a lot cheaper than the $120 disc?
I would also prefer if I could download windows from online somehow.

Any help would be appreciated.

I do have windows 8.1 on parallels. But I have no idea what the product key was... I got it so long ago.
How would I even go about getting windows 7 from microsoft? I looked everywhere on their website but couldn't find it.

Where could I get a windows 7 key?

I added you to my contacts but I cannot seem to find a way to pm you

Would you happen to know how to turn that on?

I turned everything on I could but still nothing, is there another place I can contact you?