HDD missing Local Disk,800GB+ gone.

[pavle2222]

I just used my own USB to install Windows 8.1 (64bit) on my new 1 TB HDD.
I allocated 130 GB for C: and the rest (870GB) on D: ,the installation went well (had to use the shift+f10 trick while it was loading,though) And the computer seems fine....or at least,that's what i thought. I opened up My Computer and realized that D: is absolutely gone! There's just C: and the D: was my USB that i used to transport some stuff from the old HDD (not the boot USB,i took that one out after the files were done unpacking),i downloaded Lightshot so here's a printscreen of the problem : http://prntscr.com/a2yqzz You can't see the D: USB here because i took it out.
So,where has 80% of my HDD disappeared to? If the answer is nowhere to be found,i can always just install Windows 8 again,of course,but i'd rather keep that option as a fail-safe.
Also,as an update,my PC specs are as follows:
CPU : FX 6300
GPU : R9 380X (Gigabyte)
RAM : 2X4GB 1333Mhz
If you need further details,i'll answer whatever.
I'll be checking up on the thread every 2-5 hours.

 

[smorizio]

use windows diskmanagemt make sure you give the new partion a drive letter and the partion is active and formatted.

 

[pavle2222]

use windows diskmanagemt make sure you give the new partion a drive letter and the partion is active and formatted.

I'm guessing diskmanagemt is accessed through cmd,actually,no,it seems not.
How do i access it? And with the second update,i actually found it with a quick google search.
And with the third update,thank you very much,i have fixed it. http://prntscr.com/a2yv8v