how do i open a word doc from a flash drive using office for iMac?

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To open a Word document from a USB drive, do it as you would do if the document is stored on the hard disk. Just double-click it and Microsoft Word should open with this document. If another application is opened or it doesn't open, right-click the file, select "Open with" and choose Microsoft Word

1. Open Word. Select Open from Word's File menu. Locate the file on the flash drive, select it, click on the Open button.
2. Double-click on the document which should open it in Word automatically.

Click on the desktop and go to Finder>Preferences. Check the General and Sidebar tabs to make sure 'external disks' is checked.

Try showing external drives in Desktop. Open Finder, go to Finder menu (on the menu bar) > Preferences > General, and tick "External drives". Then, connect the USB drive and it should show up in Desktop. Double-click it and open your Word document

Please, in the future provide the full information about your problem. You never stated that the flash drive did not appear on your Desktop. That is essential information for solving your problem as opposed to how to actually open a file. 🙂