Hi! How do I generate References using EndNote 6 from a document that have been typed before the installation of EndNote?

I suggest that you read the getting started guide.  There is no magic way to get citations and a bibliography into a document already written.   You need to import or enter the information for each of the references in the paper and then insert the citations in the document basically linking each of the citations to the records in the library.  There are ways to convert a bibliogrpahy into a tagged format that might be importable into an endnote library. You might want to read this thread to see some ideas and then decide whther it is worth the time investment.