how to get the box back after you have clicked off the circle

As long as you haven't done anything else, press the F9 key.

thank you 

HOW TO UNPAIR  and move the window 

I am not entirely sure if I know what you mean, but I would get rid of that circle that you don't need anymore;

Go into Edit Mode, hover your mouse pointer over a vertex (point) of the circle and press L followed by X:

Then select all ( A) and press P > Separate by Loose Parts:

Then, in Object Mode you should have something like this:

A rocket body and a separate window...