Although Word has so-called 'Chicago' citation and bibliography fields, their formats don't conform to either of the Chicago referencing styles.
Aside from that, MS also hasn't provided any tools for taking an existing set of references and importing them into Word's Sources.xml file (that's where it stores references).
Given the faulty nature of the Chicago referencing in Word, what I do is:
• create each reference entry manually, via References>Manage Sources>New;
• insert the citation and bibliography fields as per normal, via References; and,
• when I'm done editing the document, convert the fields to plain text so I can correct their formats.
It's a pain, and I wish MS would get such basic things right instead of foisting half-baked tools like this on the public, but the approach I take allows me to at least maintain the references in Word and the conversion process is quicker than doing each entry from scratch one at a time.
There is also a third-party Addin for Word, named EndNote (
http://endnote.com/), which I believe does a much better job of the reference formatting and allows references to be imported from various sources. I don't know whether references can be imported from an ordinary document, though, and AFAIK doesn't make any use of references you might already have added to Word.