Resizing Window/Viewport

Operating system: MacOS
Slicer version: Latest

Hi all,
I’m new to 3D slicer. Could someone point me toward how to correctly resize my window/viewport/slice?

In the bottom left green panel I see the image is there. However the image is cropped too much. When I scroll the viewport/window slides horizontally. I expect it to be full size and when I scroll for it to progress through the images/slices.

Thanks for your help tremendously!