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.
Edit mode, select all faces and unwrap. Select all in UV editor and place the UV island to cover the image.
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.