1. You will need to move the window back to the correct position by pressing the windows key (on your keyboard) plus one of the arrow keys until the window is in the correct position on your screen. (Choose whichever arrow key that corresponds to the direction you need to move the window).


Examples:

Windows logo key Picture of Windows logo key  + Up Arrow 
Windows logo key Picture of Windows logo key  + Left Arrow
Windows logo key Picture of Windows logo key  + Right Arrow
Windows logo key Picture of Windows logo key  + Down Arrow

2. If this does not work, you can try right clicking on the toolbar at the bottom of your screen and clicking on "show windows side by side"