Many of us have WORD documents that we have been using in our classes. Since the move to Google Drive, the question has come up - "How do I convert my WORD Docs into a Google Doc?"
This may be because now you'd like to share it or collaborate on it with others, or perhaps you'd like to share the document contents with your class via Doctopus.
The process is relatively simple. Once you start doing it regularly, it will become clear to you.
And, by the way, you haven't lost your WORD document. You can still access it in WORD, or in Google using that "Open With" option.
Here's a good little video by Richard Byrne from Free Technology for Teachers that will show you how simple it is.