Click and Drag
To edit the width of a column, click on an element in the column, then click and drag the dotted lines on the left or right of the column to the desired size.
The column will automatically change size as you drag its sides.
Column sizes can be adjusted to pre-determined intervals. For example, a column can be 1/8, 1/4, 1/3, 1/2, 2/3, etc.