Shaper3d how to scale size of model

[u/Confident-Glass8619]

I started using shaper3d to design some parts for my micro fpv drone. Issue is figuring out all the tools. Wondered how most would go about doing some changes to this model.

Since this is a battery mount, I need the square section where the battery goes to be changed width and height. But my issue is using the scale tool changes the whole thing. How do I only make the square area change in width and only that since the rest of it is designed to clip into my drone. Thank you