Changing column widths

I am trying to change column width on a page.

In your Help section it says to “Click and drag the margin space in between two columns to change the column widths.” – that sounds great, except it’s not working for me. Am I missing something? I am using just regular ol’ Make, not Make Plus.

I am trying to have a central section that spans 2/3 of the page and a second section to the right that spans the remaining 1/3. Thanks!