1) Revise that the external hard drive is empty becuase once you will begin the partition process all data on that drive will be erased completely.
2) From the Micrsosoft console type MMC, this from the Windows start menu.
3) Add the Disk Manager snap-in. This can be also done from File menu and select add napp-in. Click Disk manager from the list.
4) Right-click on the disk in the list of disk at the bottom of the snap-in. You will see a short-cut menu which will give you different options in reference to the partition drive. Here you have the option of either:Expand the partition, delete the partition or shrink the partition. Also you get the possibility of check this as a primary partition if you wish to.
5) Here you can format the new partitions where you utilize the same short-cut menu. In here you must format all partitions you intend to use. It is also an option to set this using the drive letters, this way your operating system will recognize which drive is which letter.