Welcome to the Community.
You may have to reformat the hard drive to begin with as most WD My Book drives come Windows-ready:
http://wdc.custhelp.com/app/answers/detail/a_id/3865/
However, please bear in WD does not support using WD USB drives on non-WD routers. As such they are not tested for compatibility. If you need a wireless backup solution I would recommend a WD My Book Live or a WD My Cloud instead.
Regards,
