Getting 500gb WD Blu to work as secondary

So i have been using an SSD to store all my stuff and now came the point where i need more storage. I hooked up the WD hard drive and in windows it does not show up as a secondary drive, BTW the WD drive has a copy of win 8.1 on it, also i was not able to boot from the drive but my motherboard does recognize that the drive is there. Do i have to clear the drive? i don't know please help!

Is your primary os on the ssd?

Go into Disk Management and format the WD Blue drive.  If you need to backup any data from it, assign a drive letter to it and get your stuff off before formatting.

Yes my primary Win 8.1 is on my 120gb Samsung 840 Evo