I set up my blog using a pre-existing template in Blogspot and it's supposed to be customizable but I can't figure it out.

The layout has a main section and a sidebar to the right and I'd like to increase their width to have more space

variables are defined like this in the head of the document

/* Variable definitions
====================
<Variable name="mainBgColor" description="Main Background Color"
type="color" default="#ffffff" value="#ffffff">

It is combined with CSS to define the width of the sections

then in the body, elements are called for in

<b:widget id='BlogArchive1'

I am pretty lost