Explanation

The keyboard shortcut to open an existing file in Microsoft Word is Ctrl+O.

You can also open a document in Word by double-clicking its icon in Windows. 

Here are some other keyboard shortcuts for Microsoft Word: 

Ctrl+N: Opens a new or blank document

Ctrl+S: Saves the document

Ctrl+W: Closes the document

Ctrl+A: Selects all contents of the page

Ctrl+B: Bolds highlighted selection

Ctrl+C: Copies selected text

Ctrl+X: Cuts selected text

Ctrl+P: Opens the print window