G'Day Debby,
You can set Word so that, when you Edit, Word...
EITHER Overtypes
OR Inserts
....as you type new text.
You appear to have it set to Overtype.
Try:
Tools>Options
Edit (Tab)
Make sure that both boxes...
Use INS key for paste
Overtype mode
...are UNCHECKED.
With these settings...
a. Word will normally insert as you type new text AND
b. You can switch to Overtype (and back) using
the Insert key on the keyboard.
In the Word status bar, at the bottom of the Word window,
you will see a 'grayed out' OVR. When you press Insert,
this will become 'black' to indicate Overtype mode, press
Insert again to 'gray' it and return to Insert mode.