How do I reformat my WD Elements?

How do I reformat my WD Elements?  My Mac suddenly doesn’t regognize it anymore.

Steps on how to format the drive are provided on the following link:

How to partition and format a WD drive on Windows (8, 7, Vista, XP) and Mac OSX

http://wdc.custhelp.com/app/answers/detail/a_id/3865