How to reset WD My Book Essential and start install over?

WD Software & Mobile Apps WD Software
6

I thought you said you were able to see it, but not access it.  So, you don’t see it in Disk Utility?  Did you ever reformat it before attempting to use it on your Mac?  The drive comes formatted with NTFS.  That’s a Windows format.  The Mac can see it, but not write to it.  If it shows up in Disk Utility, then you can try to reformat it in HFS+, and see if that makes it readable and writeable.