"HD full" message appearing on my screen when working a document
I keep getting a "HD full" message in a pop up window when working in Word documents. It pops up rather very often and is incredibly annoying. What can I do to free space? How do I do it? I am an almost 60 yr old humble computer and internet neophyte. Therefore, a tutorial or specific instructions will be highly appreciated.
MacBook Air, OS X Mavericks (10.9.5)