If you already have one column and want to add another you can select the
entire column and drag out a duplicate using Ctrl-D. Keep the selection
active of the new column and move it into place with the mouse and arrow
("nudge") keys.
If you don't already have a column and are creating one for the first time
use the Align and Distribute features to get things lined up nicely. It
helps to if you have your Snap settings set to snap to Geometry. This will
allow one shape to "snap" to the position of another.
