James:
Perhaps at this point you've received sufficient information here to have resolved your problem. If that is the case, read no further...
But if you still need some more info and/or help...
1. First of all you should be clear as to what specifically is your objective. You say you're planning to buy a new HDD.
But what for? Are you planning to use that drive as a secondary drive in your system for storage and/or backup purposes?
Or are you planning to use that drive to replace your existing system drive - your boot drive?
2. What are you working with - a desktop PC - a laptop?
We'll assume for the moment that you're planning to use the new HDD as a secondary drive. I assume you're working with a desktop PC.
1. You'll install the drive in the PC, connecting it to an appropriate SATA connector on the motherboard and connecting power to the disk.
2. Presumably the HDD you will be purchasing is a "virgin" disk. So when you boot the system with that HDD connected a Windows "Initialize Disk" message may appear indicating you must "initialize" the disk before it can be utilized by the system.
If the Initialize Message does not appear it will ordinarily do so when you access Disk Management.
Assuming the disk-capacity of the new drive is not greater than 2 TB the MBR partition style option will be the default. Click OK and the disk will be initialized.
3. If, for some reason, the Initialize Message does not appear, access Disk Management. If the disk has not been initialized you will note that in the gray box that's at the far left of the graphic that lists the drive there's a small red arrow pointing downward that's next to the Disk number. That's a signal that the drive has not been initialized.
Right-click on the gray box and select the "Initialize Disk" option. The Initialize Disk window will appear and you can then click OK.
4. The disk will be shown as "Unallocated" in Disk Management. You can then proceed with creating one or more partitions (volumes) so that the disk will be fully recognized by the system.