Dimension Driven Weldment Sketch

I have a simple crate made with 3D sketches and weldments.

I want to set up a table where I can change a couple dimensions on the sketch to resize it.

I simply do not know how to do that. What function should I be looking for to help me do this.

This is also my first foray into weldments but I think I have that figured out.

SolidworksAssemblies