I'm buying a house and at one point and time it had an addition put on the back of it but the oddest thing was they left the windows and a door from the old home.

So now I have two windows that of you look through them you see the addition and a door that is right next to the breezeway. One window is in the bathroom by the tub of you look out the window you can see the kitchen

What I'm wanting to do is cover them so it looks like a wall on both sides. Going back to the home Monday to get measurements for the new flooring so I'll take photos of the problem area to let you all see. Thanks!

Sounds to me like rip them out , frame them in, hang drywall, finish and paint.

^^^^^^^

Yeah you don't cover them, you take them out

You could tape newspaper to the inside.
But sadly that would also mean you should take apart your air conditioner at night during the winter.
While still on the roof.

There is no other reasonable way to do this.

If the addition were an enclosed porch or patio,...

I don't know why? There is also the old back door!