That depends somewhat on the capacity of the drive and the interface technology. The Xbox One requires USB 3.0 connected hard drives (it is NOT backwards compatible) and is limited to three total drives (including the internal). The drive must be at least 256GB in size and must be formatted as "storage" to store games and apps.
USB hard drives usually have a cable with a blue tongue on the computer end and the end that connects to the drive will often be an oddly tall or wide USB connector.