If you want to install it wirelessly, then follow the directions in your user manual, starting at page 7 and/or 18:
http://www.wdc.com/wdproducts/library/UM/ENG/4779-705118.pdf
Before using, make sure it is formatted for Mac using Disk Utility (in your Applications > Utilities folder): Mac OS Extended (Journaled) and, in the Partition tab under Option: GUID Partition Scheme.
If you want to use it with the included USB cable, then plug it into your Macbook Pro and use Disk Utility to format it.
FWIW, it is best to have an empty external hard drive when using it for backups; however, for your wireless setup you need to have that WD software on it (I guess). And, backups are more reliable when done via a cable rather than wirelessly (which also can be extremely slow).