Even if you normally use Microsoft Word, please consider using LibreOffice Writer for this project. The advantage of LibreOffice Writer is that its native file format is OpenDocument Format, which is an open file format. More specifically, LibreOffice Writer uses OpenDocument Text (ODT) as its native file format.
If using LibreOffice Writer isn't an option for you or you simply prefer to use Microsoft Word, there are two main cases to consider:
You use Microsoft Word for Windows
You use Microsoft Word for Macintosh
In either case, the recommended strategy is to avoid the legacy file formats DOC and RTF as much as possible because neither DOC nor RTF is an open file format. :-(
Please download the .zip file below, unzip it, and read README.TXT, which is (hopefully) self-explanatory. Note that you'll still need the style sheet.
Microsoft Word for Windows
Beginning with Microsoft Office 2007 SP2, Word can read and save to .odt files, :-) which means that you can use the format ODT the whole time when writing your paper and should never have to save to the formats DOC or RTF. If at all possible, please use Office 2007 SP2 or higher and save to the format ODT. In this case, the subdirectory ODT (in the .zip file) is relevant.
If your only option is to use Microsoft Office 2003, the best choice is to save to the format DOCX (a.k.a. Office Open XML). In this case, the subdirectory DOCX is relevant. Again, please try to avoid DOC and RTF the whole time.
Microsoft Word for Macintosh
Unfortunately, to the best of my knowledge, no version of Microsoft Office for Macintosh can read or save to .odt files. :-( (So much for feature compatibility between Microsoft Office for Windows and for Mac ...) This means that the best option is use DOCX, hence the subdirectory DOCX is relevant. (Beginning with Microsoft Office 2004 for Macintosh, Word can read and save to .docx files.) Again, please try to avoid DOC and RTF the whole time.
Note: Since I don't own a copy of Microsoft Word or use it, my only access to Word is on public computers or on colleagues' computers, so it may not be easy for me to answer specific questions about Word. :-( However, if something is unclear, please don't hesitate to ask – I can always try to answer. :-)
Note added on 2016/03/04: Beginning with v1.0c of the EISS LibreOffice Writer style package (see the sidebar), two (untested) DOC files are provided, so there's no need for a separate EISS Microsoft Word style package (the last version was v1.0b). I've left the text above for the historical record, but I never really supported Microsoft Word anyway, and the text above was simply a long-winded and indirect way of saying this. :-)