for some reason I am getting a black flashing box over the letter and when I type it overtypes each character instead of inserting a character
In the bottom of Writer’s window (I assume you’re using Writer – you don’t specify), you probably see the word “Overwrite” just on the right of the mid-point of that bottom status bar.
If you hover your “pointer” over it, you’ll see “Overwrite mode. Click to change to insert mode.” So –
click it, and you’ll have the insert mode.
Your keyboard may also have a toggle for this, but you haven’t told us what you’re using (OSX? Win? LInux?), and that makes a difference here.
Hopefully, that bottom-status-bar toggle will be sufficient, though.
Hsve you tried pressing the “Insert” key on your keyboard?
If AnnaP’s got an “Insert” key, of course.