You can create a Google Doc by uploading an existing Word, Power point or Excel file. You will simply follow these few steps: click on the Google Apps symbol, Select the red upload arrow (next to create), Choose the file to upload and upload it, locate the uploaded file in the list of files in "My Drive", right click on the document's file name, choose "Open with" and then choose Google Docs (or Google presentation for a Power Point or Google spreadsheet for an Excel File). You can now edit and revise that document via Google Drive