|Connect the external to a working USB port. Then go to Windows Disk Management. The drive should show there. If it is already partitioned and formatted, delete the partition and create a new partition of the size you want. Then you can either partition the remaining space as desired or format the first partition and proceed from there. |
The only confusing part is the large number you will see for the total space. If you write that number down you can do the math to get it right.
You can also assign/re-assign drive letters to the newly created partitions to suit. If the drive will only be connected intermittently I suggest using letters near the end of the alphabet so that when you connect other mass storage devices they don't use the same drive letters temporarily.
The default format type will be NTFS, which is fine, unless you need to use the external on non-Windows systems.