Welcome to the community, RabbitDen!
I'm sorry to hear about your connectivity issues with your second WD Blue! I'd recommend you to try using a different SATA cable and plugging it to a different SATA port. I'd also advise you to check if it's recognized in BIOS and Device Manager.
When going into Disk Management, you can try clicking on 'Rescan Disks', hopefully, this would make the secondary HDD pop up. Another thing that might help you recognize it is resetting BIOS, but you'd need to reconfigure all the settings afterward because it would get them back to factory defaults. Here are a couple of methods you can use:
http://www.wikihow.com/Reset-Your-BIOS
As for initializing & formatting the drive through Disk management, you can...