How to change width of side columns?

How do I change the width of the side columns using the ‘Electro’ template?

i do believe you change the column widths with the CSS stylesheet. Press control key plus the letter F and typed in “fixed”, this should take you to the section where you should see column settings. if you have a unfixed layout, then the controls will be above or below the fixed controls.

pm me if you need more details.