I am not sure whether I am taking the right path. From guides on the internet I got this far. How to apply the texture on the left window to the plane of the right viewport ? Thanks.
Select the points in the UV editor, rotate, scale, and position it to cover the image.
Add a material that uses the image as a texture, and switch to material preview or rendered mode.
I think I got it almost right. But as you see, I am not able to adjust the tiles in the UV editor. Instead the brush is dominating that part of the screen. Please see