Endnote can't EndNote cannot directly import existing bibliographies (eg e.g. typed in a Word document) because it doesn't does not know how to break down the references into their component parts (author, year, title, etc). However there are some tools that can convert a bibliography into a format Endnote EndNote can use.
One is Ref2RIS (for Macs, but the page also lists some web-based tools and some methods for converting from Access or Excel format).