If you have a computer with Windows XP or above OS, then open Computer or My Computer and locate the external hard drive. Right-click on the external hard drive and choose format. Click the drop-down arrow on the File window and select NTFS.
The rest is obvious.
You can also right-click Computer/My Computer and click Manage...
In the window that opens, you can select Disk Management and do the formatting for the external hard disk there.