You will need to know which version of Microsoft Word you are running to determine which Ebsta install to download.
To find out which version of Word you are running, please refer to this article by Microsoft:
Word 2007
Word 2007 runs 32-bit so you will need to use this install:
http://install.ebsta.com/word/x86/WordEbsta.msi
Word 2010 or 2013
If you have Word 2010 or 2013 32-bit, use this install link:
http://install.ebsta.com/word/x86/WordEbsta.msi
If you have Word 2010 or 2013 64-bit, use this install link: